Apparatus, system, and method for accessing memory

ABSTRACT

Apparatuses, systems, methods, and computer program products are disclosed for providing access to auto-commit memory. An auto-commit memory module is configured to cause a volatile memory buffer to commit data from the volatile memory buffer to a non-volatile memory medium in response to a trigger. A mapping module is configured to determine whether to associate a range of data with the volatile memory buffer. A bypass module is configured to service a request for the range of data directly from the volatile memory buffer in response to the mapping module determining to associate the range of data with the volatile memory buffer.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application:

-   -   is a continuation-in-part of and claims priority to U.S. patent        application Ser. No. 13/694,000, now U.S. Pat. No. 9,047,178,        entitled “APPARATUS, SYSTEM, AND METHOD FOR AUTO-COMMIT MEMORY        MANAGEMENT” and filed on Dec. 4, 2012 for Nisha Talagala, et        al.;    -   claims the benefit of U.S. Provisional Patent Application No.        61/705,058 entitled “APPARATUS, SYSTEM, AND METHOD FOR SNAPSHOTS        IN A STORAGE DEVICE” and filed on Sep. 24, 2012 for Nisha        Talagala, et al.;    -   claims the benefit of U.S. Provisional Patent Application No.        61/691,221 entitled “APPARATUS, SYSTEM, AND METHOD FOR        AUTO-COMMIT MEMORY” and filed on Aug. 20, 2012 for Nisha        Talagala, et al.;    -   claims the benefit of U.S. Provisional Patent Application No.        61/661,742 entitled “APPARATUS, SYSTEM, AND METHOD FOR        AUTO-COMMIT MEMORY” and filed on Jun. 19, 2012 for Nisha        Talagala, et al.;    -   claims the benefit of U.S. Provisional Patent Application No.        61/637,257 entitled “APPARATUS, SYSTEM, AND METHOD FOR        AUTO-COMMIT MEMORY” and filed on Apr. 23, 2012 for David Flynn,        et al.;    -   claims the benefit of U.S. Provisional Patent Application No.        61/583,133 entitled “APPARATUS, SYSTEM, AND METHOD FOR        AUTO-COMMIT MEMORY” and filed on Jan. 4, 2012 for David Flynn,        et al.;    -   is a continuation-in-part application of and claims priority to        U.S. patent application Ser. No. 13/324,942, now U.S. Pat. No.        8,527,693, entitled “APPARATUS, SYSTEM, AND METHOD FOR        AUTO-COMMIT MEMORY” and filed on Dec. 13, 2011 for David Flynn,        et al.; and    -   claims the benefit of U.S. Provisional Patent Application No.        61/422,635 entitled “APPARATUS, SYSTEM, AND METHOD FOR        AUTO-COMMIT MEMORY” and filed on Dec. 13, 2010 for David Flynn,        et al., each of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to auto-commit memory and more particularly toan interface for accessing auto-commit memory.

BACKGROUND

Volatile memory such as random access memory (RAM) typically has fasteraccess times than non-volatile storage, such as NAND flash, magnetichard disk drives, or the like. While the capacities of volatile memorycontinue to increase as the price of volatile memory decreases, volatilememory remains more expensive per unit of capacity than mostnon-volatile storage.

This often leads to design tradeoffs between the speed and performanceof volatile memory and the lower price of non-volatile storage at largercapacities. Further, to achieve the speed and performance benefits ofvolatile memory, a system typically sacrifices the persistence ofnon-volatile memory, causing data to be irretrievably lost withoutpower.

SUMMARY

Methods for providing access to auto-commit memory are presented. In oneembodiment, a method includes receiving a request for data. A request,in certain embodiments, includes a namespace identifier. A method, inone embodiment, includes identifying a relationship between a namespaceidentifier and a memory. In one embodiment, a method includes satisfyinga request using a memory without passing the request through anoperating system storage stack in response to an identified relationshipassociating a namespace identifier with the memory.

Apparatuses for providing access to auto-commit memory are presented. Inone embodiment, an auto-commit memory module is configured to cause avolatile memory buffer to commit data from the volatile memory buffer toa non-volatile memory medium in response to the data filling thevolatile memory buffer. A mapping module, in a further embodiment, isconfigured to determine whether to associate a range of addresses fordata with a volatile memory buffer. In certain embodiments, a bypassmodule is configured to service a request for a range of addresses fordata directly from a volatile memory buffer in response to anauto-commit mapping module determining to associate a range of addressesfor data with the volatile memory buffer.

An apparatus, in one embodiment, includes means for associating alogical identifier with a page of volatile memory. In a furtherembodiment, an apparatus includes means for bypassing an operatingsystem storage stack to satisfy a storage request for data of a page ofvolatile memory directly. In certain embodiments, an apparatus includesmeans for preserving data of a page of volatile memory in response to afailure condition.

Systems for providing access to auto-commit memory are presented. In oneembodiment, a system includes a recording device comprising one or moreauto-commit pages configured to preserve data of the auto-commit pagesin response to a restart event. A system, in a further embodiment,includes a device driver for a recording device. A device driver, incertain embodiments, is configured to cause data of auto-commit pages tobe mapped, from kernel-space, into virtual memory. A device driver, inone embodiment, is configured to service requests, from user-space, fordata of auto-commit pages.

Computer program products comprising a computer readable storage mediumstoring computer usable program code executable to perform operationsfor providing access to auto-commit memory is also presented. In oneembodiment, an operation includes intercepting, in user-space, a storagerequest for a memory device. A storage request, in certain embodiments,comprises a file identifier and an offset. An operation, in a furtherembodiment, includes servicing a storage request in user-space directlyfrom a volatile memory of a memory device in response to determiningthat an offset and a file identifier are mapped to the volatile memory.An operation, in one embodiment, includes mapping an offset and a fileidentifier to a volatile memory in response to determining that a fileidentifier is not mapped to the volatile memory.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of this disclosure will be readilyunderstood, a more particular description of the disclosure brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the disclosure and are nottherefore to be considered to be limiting of its scope, the disclosurewill be described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 is a schematic block diagram illustrating one embodiment of asystem for auto-commit memory;

FIG. 2 is a block diagram of one embodiment of an auto-commit memory;

FIG. 3 is a block diagram of another embodiment of an auto-commitmemory;

FIG. 4 is a block diagram of a system comprising a plurality ofauto-commit memories;

FIG. 5 is a block diagram of an auto-commit memory implemented with acommit management apparatus;

FIG. 6 is a block diagram of another embodiment of a system comprisingan auto-commit memory;

FIG. 7 is a flow diagram of one embodiment of a method for providing anauto-commit memory;

FIG. 8 is a flow diagram of another embodiment of a method for providingan auto-commit memory;

FIG. 9 is a flow diagram of another embodiment of a method for providingan auto-commit memory;

FIG. 10A is a schematic block diagram illustrating one embodiment of anauto-commit memory module;

FIG. 10B is a schematic block diagram illustrating another embodiment ofan auto-commit memory module;

FIG. 11 is a schematic block diagram illustrating one embodiment of amapping structure, a sparse logical address space, and a log-basedwriting structure;

FIG. 12 is a schematic flow chart diagram illustrating one embodiment ofa method for providing access to auto-commit memory; and

FIG. 13 is a schematic flow chart diagram illustrating anotherembodiment of a method for providing access to auto-commit memory.

DETAILED DESCRIPTION

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the present disclosure should be or are in anysingle embodiment of the disclosure. Rather, language referring to thefeatures and advantages is understood to mean that a specific feature,advantage, or characteristic described in connection with an embodimentis included in at least one embodiment of the present disclosure. Thus,discussion of the features and advantages, and similar language,throughout this specification may, but do not necessarily, refer to thesame embodiment.

Furthermore, the described features, advantages, and characteristics ofthe disclosure may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize that thedisclosure may be practiced without one or more of the specific featuresor advantages of a particular embodiment. In other instances, additionalfeatures and advantages may be recognized in certain embodiments thatmay not be present in all embodiments of the disclosure. These featuresand advantages of the present invention will become more fully apparentfrom the following description and appended claims, or may be learned bythe practice of the disclosure as set forth hereinafter.

Many of the functional units described in this specification have beenlabeled as modules, in order to more particularly emphasize theirimplementation independence. For example, a module may be implemented asa hardware circuit comprising custom VLSI circuits or gate arrays,off-the-shelf semiconductors such as logic chips, transistors, or otherdiscrete components. A module may also be implemented in programmablehardware devices such as field programmable gate arrays, programmablearray logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of executable code may be a single instruction, or manyinstructions, and may even be distributed over several different codesegments, among different programs, and across several memory devices.Similarly, operational data may be identified and illustrated hereinwithin modules, and may be embodied in any suitable form and organizedwithin any suitable type of data structure. The operational data may becollected as a single data set, or may be distributed over differentlocations including over different storage devices, and may exist, atleast partially, merely as electronic signals on a system or network.Where a module or portions of a module are implemented in software, thesoftware portions are stored on one or more computer readable media.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

Reference to a computer readable medium may take any form capable ofstoring machine-readable instructions on a digital processing apparatus.A computer readable medium may be embodied by a compact disk,digital-video disk, a magnetic tape, a Bernoulli drive, a magnetic disk,a punch card, flash memory, integrated circuits, or other digitalprocessing apparatus memory device.

Furthermore, the described features, structures, or characteristics ofthe disclosure may be combined in any suitable manner in one or moreembodiments. In the following description, numerous specific details areprovided, such as examples of programming, software modules, userselections, network transactions, database queries, database structures,hardware modules, hardware circuits, hardware chips, etc., to provide athorough understanding of embodiments of the disclosure. One skilled inthe relevant art will recognize, however, that the disclosure may bepracticed without one or more of the specific details, or with othermethods, components, materials, and so forth. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the disclosure.

The schematic flow chart diagrams included herein are generally setforth as logical flow chart diagrams. As such, the depicted order andlabeled steps are indicative of one embodiment of the presented method.Other steps and methods may be conceived that are equivalent infunction, logic, or effect to one or more steps, or portions thereof, ofthe illustrated method. Additionally, the format and symbols employedare provided to explain the logical steps of the method and areunderstood not to limit the scope of the method. Although various arrowtypes and line types may be employed in the flow chart diagrams, theyare understood not to limit the scope of the corresponding method.Indeed, some arrows or other connectors may be used to indicate only thelogical flow of the method. For instance, an arrow may indicate awaiting or monitoring period of unspecified duration between enumeratedsteps of the depicted method. Additionally, the order in which aparticular method occurs may or may not strictly adhere to the order ofthe corresponding steps shown.

FIG. 1 depicts one embodiment of a system 100 for data and/or powermanagement in the event of a power failure, power reduction, or otherpower loss. In the depicted embodiment, the system 100 includes a hostcomputing device 114 and a storage device 102. The host 114 may be acomputer such as a server, laptop, desktop, or other computing deviceknown in the art. The host 114 typically includes components such asmemory, processors, buses, and other components as known to those ofskill in the art.

The host 114 stores data in the storage device 102 and communicates datawith the storage device 102 via a communications connection (not shown).The storage device 102 may be internal to the host 114 or external tothe host 114. The communications connection may be a bus, a network, orother manner of connection allowing the transfer of data between thehost 114 and the storage device 102. In one embodiment, the storagedevice 102 is connected to the host 114 by a PCI connection such as PCIexpress (PCI-e). The storage device 102 may be a card that plugs into aPCI-e connection on the host 114.

The storage device 102 also has a primary power connection 130 thatconnects the storage device 102 with a primary power source thatprovides the storage device 102 with the power that it needs to performdata storage operations such as reads, writes, erases, etc. The storagedevice 102, under normal operating conditions, receives the necessarypower from the primary power source over the primary power connection130. In certain embodiments, such as the embodiment shown in FIG. 1, theprimary power connection 130 connects the storage device 102 to the host114, and the host 114 acts as the primary power source that supplies thestorage device 102 with power. In certain embodiments, the primary powerconnection 130 and the communications connection discussed above arepart of the same physical connection between the host 114 and thestorage device 102. For example, the storage device 102 may receivepower over a PCI connection.

In other embodiments, the storage device 102 may connect to an externalpower supply via the primary power connection 130. For example, theprimary power connection 130 may connect the storage device 102 with aprimary power source that is a power converter (often called a powerbrick). Those in the art will appreciate that there are various ways bywhich a storage device 102 may receive power, and the variety of devicesthat can act as the primary power source for the storage device 102.

The storage device 102 provides nonvolatile storage, memory, and/orrecording media 110 for the host 114. FIG. 1 shows the storage device102 comprising a write data pipeline 106, a read data pipeline 108,nonvolatile memory 110, a storage controller 104, an auto-commit memory1011, and a secondary power supply 124. The storage device 102 maycontain additional components that are not shown in order to provide asimpler view of the storage device 102.

The nonvolatile memory 110 stores data such that the data is retainedeven when the storage device 102 is not powered. Examples of nonvolatilememory 110 include flash memory, nano random access memory (nano RAM orNRAM), nanocrystal wire-based memory, silicon-oxide based sub-10nanometer process memory, graphene memory,Silicon-Oxide-Nitride-Oxide-Silicon (SONOS), Resistive random-accessmemory (RRAM), programmable metallization cell (PMC),conductive-bridging RAM (CBRAM), magneto-resistive RAM (MRAM), dynamicRAM (DRAM), phase change RAM (PRAM), or other non-volatile solid-statestorage media. In other embodiments, the non-volatile memory 110 maycomprise magnetic media, optical media, or other types of non-volatilestorage media. For example, in those embodiments, the non-volatilestorage device 102 may comprise a hard disk drive, an optical storagedrive, or the like.

While the non-volatile memory 110 is referred to herein as “memorymedia,” in various embodiments, the non-volatile memory 110 may moregenerally comprise a non-volatile recording media capable of recordingdata, the non-volatile recording media may be referred to as anon-volatile memory media, a non-volatile storage media, or the like.Further, the non-volatile storage device 102, in various embodiments,may comprise a non-volatile recording device, a non-volatile memorydevice, a non-volatile storage device, or the like.

The storage device 102 also includes a storage controller 104 thatcoordinates the storage and retrieval of data in the nonvolatile memory110. The storage controller 104 may use one or more indexes to locateand retrieve data, and perform other operations on data stored in thestorage device 102. For example, the storage controller 104 may includea groomer for performing data grooming operations such as garbagecollection.

As shown, the storage device 102, in certain embodiments, implements awrite data pipeline 106 and a read data pipeline 108, an example ofwhich is described in greater detail below with regard to FIG. 3. Thewrite data pipeline 106 may perform certain operations on data as thedata is transferred from the host 114 into the nonvolatile memory 110.These operations may include, for example, error correction code (ECC)generation, encryption, compression, and others. The read data pipeline108 may perform similar and potentially inverse operations on data thatis being read out of nonvolatile memory 110 and sent to the host 114.

The storage device 102 also includes a secondary power supply 124 thatprovides power in the event of a complete or partial power disruptionresulting in the storage device 102 not receiving enough electricalpower over the primary power connection 130. A power disruption is anyevent that unexpectedly causes the storage device 102 to stop receivingpower over the primary power connection 130, or causes a significantreduction in the power received by the storage device 102 over theprimary power connection 130. A significant reduction in power, in oneembodiment, includes the power falling below a predefined threshold. Thepredefined threshold, in a further embodiment, is selected to allow fornormal fluctuations in the level of power from the primary powerconnection 130. For example, the power to a building where the host 114and the storage device 102 may go out. A user action (such as improperlyshutting down the host 114 providing power to the storage device 102), afailure in the primary power connection 130, or a failure in the primarypower supply may cause the storage device 102 to stop receiving power.Numerous, varied power disruptions may cause unexpected power loss forthe storage device 102.

The secondary power supply 124 may include one or more batteries, one ormore capacitors, a bank of capacitors, a separate connection to a powersupply, or the like. In one embodiment, the secondary power supply 124provides power to the storage device 102 for at least a power hold-uptime during a power disruption or other reduction in power from theprimary power connection 130. The secondary power supply 124, in afurther embodiment, provides a power hold-up time long enough to enablethe storage device 102 to flush data that is not in nonvolatile memory110 into the nonvolatile memory 110. As a result, the storage device 102can preserve the data that is not permanently stored in the storagedevice 102 before the lack of power causes the storage device 102 tostop functioning. In certain implementations, the secondary power supply124 may comprise the smallest capacitors possible that are capable ofproviding a predefined power hold-up time to preserve space, reducecost, and simplify the storage device 102. In one embodiment, one ormore banks of capacitors are used to implement the secondary powersupply 124 as capacitors are generally more reliable, require lessmaintenance, and have a longer life than other options for providingsecondary power.

In one embodiment, the secondary power supply 124 is part of anelectrical circuit that automatically provides power to the storagedevice 102 upon a partial or complete loss of power from the primarypower connection 130. Similarly, the system 100 may be configured toautomatically accept or receive electric power from the secondary powersupply 124 during a partial or complete power loss. For example, in oneembodiment, the secondary power supply 124 may be electrically coupledto the storage device 102 in parallel with the primary power connection130, so that the primary power connection 130 charges the secondarypower supply 124 during normal operation and the secondary power supply124 automatically provides power to the storage device 102 in responseto a power loss. In one embodiment, the system 100 further includes adiode or other reverse current protection between the secondary powersupply 124 and the primary power connection 130, to prevent current fromthe secondary power supply 124 from reaching the primary powerconnection 130. In another embodiment, the auto-commit memory 1011 mayenable or connect the secondary power supply 124 to the storage device102 using a switch or the like in response to reduced power from theprimary power connection 130.

An example of data that is not yet in the nonvolatile memory 110 mayinclude data that may be held in volatile memory as the data movesthrough the write data pipeline 106. If data in the write data pipeline106 is lost during a power outage (i.e., not written to nonvolatilememory 110 or otherwise permanently stored), corruption and data lossmay result.

In certain embodiments, the storage device 102 sends an acknowledgementto the host 114 at some point after the storage device 102 receives datato be stored in the nonvolatile memory 110. The write data pipeline 106,or a sub-component thereof, may generate the acknowledgement. It isadvantageous for the storage device 102 to send the acknowledgement assoon as possible after receiving the data.

In certain embodiments, the write data pipeline 106 sends theacknowledgement before data is actually stored in the nonvolatile memory110. For example, the write data pipeline 106 may send theacknowledgement while the data is still in transit through the writedata pipeline 106 to the nonvolatile memory 110. In such embodiments, itis highly desirable that the storage device 102 flush all data for whichthe storage controller 104 has sent an acknowledgement to thenonvolatile memory 110 before the secondary power supply 124 losessufficient power in order to prevent data corruption and maintain theintegrity of the acknowledgement sent.

In addition, in certain embodiments, some data within the write datapipeline 106 may be corrupted as a result of the power disruption. Apower disruption may include a power failure as well as unexpectedchanges in power levels supplied. The unexpected changes in power levelsmay place data that is in the storage device 102, but not yet innonvolatile memory 110, at risk. Data corruption may begin to occurbefore the auto-commit memory 1011 is even aware (or notified) thatthere has been a disruption in power.

For example, the PCI-e specification indicates that, in the event that apower disruption is signaled, data should be assumed corrupted and notstored in certain circumstances. Similar potential corruption may occurfor storage devices 102 connected to hosts 114 using other connectiontypes, such as PCI, serial advanced technology attachment (serial ATA orSATA), parallel ATA (PATA), small computer system interface (SCSI), IEEE1394 (FireWire), Fiber Channel, universal serial bus (USB), PCIe-AS, orthe like. A complication may arise when a power disruption occurs(meaning that data received from that point to the present time may bepresumed corrupt), a period of time passes, the disruption is sensed andsignaled, and the auto-commit memory 1011 receives the signal andbecomes aware of the power disruption. The lag between the powerdisruption occurring and the auto-commit memory 1011 discovering thepower disruption can allow corrupt data to enter the write data pipeline106. In certain embodiments, this corrupt data should be identified andnot stored to the nonvolatile memory 110. Alternately, this corrupt datacan be stored in the nonvolatile memory 110 and marked as corrupt asdescribed below. For simplicity of description, identifying corrupt dataand not storing the data to the nonvolatile memory 110 will be primarilyused to describe the functions and features herein. Furthermore, thehost 114 should be aware that this data was not stored, or alternativelydata for which integrity is a question is not acknowledged until dataintegrity can be verified. As a result, corrupt data should not beacknowledged.

The storage device 102 also includes the auto-commit memory 1011. Incertain embodiments, the auto-commit memory 1011 is in communicationwith, managed by, or at least partially integrated with the storagecontroller 104. The auto-commit memory 1011 may, for instance, cooperatewith a software driver and/or firmware for the storage device 102. Inone embodiment, at least a portion of the auto-commit memory 1011 isimplemented on the storage device 102, so that the auto-commit memory1011 continues to function during a partial or complete power loss usingpower from the secondary power supply 124, even if the host 114 is nolonger functioning.

In one embodiment, the auto-commit memory 1011 initiates a power lossmode in the storage device 102 in response to a reduction in power fromthe primary power connection 130. During the power loss mode, theauto-commit memory 1011, in one embodiment flushes data that is in thestorage device 102 that is not yet stored in nonvolatile memory 110 intothe nonvolatile memory 110. In particular embodiments, the auto-commitmemory 1011 flushes the data that has been acknowledged and is in thestorage device 102 that is not yet stored in nonvolatile memory 110 intothe nonvolatile memory 110. In certain embodiments, described below, theauto-commit memory 1011 may adjust execution of data operations on thestorage device 102 to ensure that essential operations complete beforethe secondary power supply 124 loses sufficient power to complete theessential operations, i.e. during the power hold-up time that thesecondary power supply 124 provides.

In certain embodiments, the essential operations comprise thoseoperations for data that has been acknowledged as having been stored,such as acknowledged write operations. In other embodiments, theessential operations comprise those operations for data that has beenacknowledged as having been stored and erased. In other embodiments, theessential operations comprise those operations for data that have beenacknowledged as having been stored, read, and erased. The auto-commitmemory 1011 may also terminate non-essential operations to ensure thatthose non-essential operations do not consume power unnecessarily and/ordo not block essential operations from executing; for example, theauto-commit memory 1011 may terminate erase operations, read operations,unacknowledged write operations, and the like.

In one embodiment, terminating non-essential operations preserves powerfrom the secondary power supply 124, allowing the secondary power supply124 to provide the power hold-up time. In a further embodiment, theauto-commit memory 1011 quiesces or otherwise shuts down operation ofone or more subcomponents of the storage device 102 during the powerloss mode to conserve power from the secondary power supply 124. Forexample, in various embodiments, the auto-commit memory 1011 may quiesceoperation of the read data pipeline 108, a read direct memory access(DMA) engine, and/or other subcomponents of the storage device 102 thatare associated with non-essential operations.

The auto-commit memory 1011 may also be responsible for determining whatdata was corrupted by the power disruption, preventing the corrupt datafrom being stored in nonvolatile memory 110, and ensuring that the host114 is aware that the corrupted data was never actually stored on thestorage device 102. This prevents corruption of data in the storagedevice 102 resulting from the power disruption.

In one embodiment, the system 100 includes a plurality of storagedevices 102. The auto-commit memory 1011, in one embodiment, managespower loss modes for each storage device 102 in the plurality of storagedevices 102, providing a system-wide power loss mode for the pluralityof storage devices 102. In a further embodiment, each storage device 102in the plurality of storage devices 102 includes a separate auto-commitmemory 1011 that manages a separate power loss mode for each individualstorage device 102. The auto-commit memory 1011, in one embodiment, mayquiesce or otherwise shut down one or more storage devices 102 of theplurality of storage devices 102 to conserve power from the secondarypower supply 124 for executing essential operations on one or more otherstorage devices 102.

In one embodiment, the system 100 includes one or more adapters forproviding electrical connections between the host 114 and the pluralityof storage devices 102. An adapter, in various embodiments, may includea slot or port that receives a single storage device 102, an expansioncard or daughter card that receives two or more storage devices 102, orthe like. For example, in one embodiment, the plurality of storagedevices 102 may each be coupled to separate ports or slots of the host114. In another example embodiment, one or more adapters, such asdaughter cards or the like, may be electrically coupled to the host 114(i.e. connected to one or more slots or ports of the host 114) and theone or more adapters may each provide connections for two or morestorage devices 102.

In one embodiment, the system 100 includes a circuit board, such as amotherboard or the like, that receives two or more adapters, such asdaughter cards or the like, and each adapter receives two or morestorage devices 102. In a further embodiment, the adapters are coupledto the circuit board using PCI-e slots of the circuit board and thestorage devices 102 are coupled to the adapters using PCI-e slots of theadapters. In another embodiment, the storage devices 102 each comprise adual in-line memory module (DIMM) of non-volatile solid-state storage,such as Flash memory, or the like. In one embodiment, the circuit board,the adapters, and the storage devices 102 may be external to the host114, and may include a separate primary power connection 130. Forexample, the circuit board, the adapters, and the storage devices 102may be housed in an external enclosure with a power supply unit (PSU)and may be in communication with the host 114 using an external bus suchas eSATA, eSATAp, SCSI, FireWire, Fiber Channel, USB, PCIe-AS, or thelike. In another embodiment, the circuit board may be a motherboard ofthe host 114, and the adapters and the storage devices 102 may beinternal storage of the host 114.

In view of this disclosure, one of skill in the art will recognize manyconfigurations of adapters and storage devices 102 for use in the system100. For example, each adapter may receive two storage devices 102, fourstorage devices 102, or any number of storage devices. Similarly, thesystem 100 may include one adapter, two adapters, three adapters, fouradapters, or any supported number of adapters. In one exampleembodiment, the system 100 includes two adapters and each adapterreceives four storage devices 102, for a total of eight storage devices102.

In one embodiment, the secondary power supply 124 provides electricpower to each of a plurality of storage devices 102. For example, thesecondary power supply 124 may be disposed in a circuit on a maincircuit board or motherboard and may provide power to several adapters.In a further embodiment, the system 100 includes a plurality ofsecondary power supplies that each provide electric power to a subset ofa plurality of storage devices 102. For example, in one embodiment, eachadapter may include a secondary power supply 124 for storage devices 102of the adapter. In a further embodiment, each storage device 102 mayinclude a secondary power supply 124 for the storage device 102. In viewof this disclosure, one of skill in the art will recognize differentarrangements of secondary power supplies 124 for providing power to aplurality of storage devices 102.

The systems, methods, and apparatus described above may be leveraged toimplement an auto-commit memory capable of implementing memory semanticwrite operations (e.g., persistent writes) at CPU memory writegranularity and speed. By guaranteeing that certain commit actions forthe write operations will occur, even in the case of a power failure orother restart event, in certain embodiments, volatile memory such asDRAM, SRAM, BRAM, or the like, may be used as, considered, orrepresented as non-volatile.

A restart event, as used herein, comprises an intentional orunintentional loss of power to at least a portion of the host computingdevice and/or a non-volatile storage device. A restart event maycomprise a system reboot, reset, or shutdown event; a power fault, powerloss, or power failure event; or another interruption or reduction ofpower. By guaranteeing certain commit actions, the auto-commit memorymay allow storage clients to resume execution states, even after arestart event, may allow the storage clients to persist differentindependent data sets, or the like.

As used herein, the term “memory semantic operations,” or moregenerally, “memory operations,” refers to operations having agranularity, synchronicity, and access semantics of volatile memoryaccesses, using manipulatable memory pointers, or the like. Memorysemantic operations may include, but are not limited to: load, store,peek, poke, write, read, set, clear, and so on. Memory semanticoperations may operate at a CPU-level of granularity (e.g., singlebytes, words, cache lines, or the like), and may be synchronous (e.g.,the CPU waits for the operation to complete). In certain embodiments,providing access at a larger sized granularity, such as cache lines, mayincrease access rates, provide more efficient write combining, or thelike than smaller sized granularity access.

The ACM may be available to computing devices and/or applications (bothlocal and remote) using one or more of a variety of memory mappingtechnologies, including, but not limited to, memory mapped I/O (MMIO),port I/O, port-mapped IO (PMIO), Memory mapped file I/O, and the like.For example, the ACM may be available to computing devices and/orapplications (both local and remote) using a PCI-e Base Address Register(BAR), or other suitable mechanism. ACM may also be directly accessiblevia a memory bus of a CPU, using an interface such as a double data rate(DDR) memory interface, HyperTransport, QuickPath Interconnect (QPI), orthe like. Accordingly, the ACM may be accessible using memory accesssemantics, such as CPU load/store, direct memory access (DMA), 3^(rd)party DMA, remote DMA (RDMA), atomic test and set, and so on. Thedirect, memory semantic access to the ACM disclosed herein allows manyof the system and/or virtualization layer calls typically required toimplement committed operations to be bypassed, (e.g., call backs viaasynchronous Input/Output interfaces may be bypassed). In someembodiments, an ACM may be mapped to one or more virtual ranges (e.g.,virtual BAR ranges, virtual memory addresses, or the like). The virtualmapping may allow multiple computing devices and/or applications toshare a single ACM address range 1021 (e.g., access the same ACMsimultaneously, within different virtual address ranges). An ACM may bemapped into an address range of a physical memory address spaceaddressable by a CPU so that the CPU may use load/store instructions toread and write data directly to the ACM using memory semantic accesses.A CPU, in a further embodiment, may map the physically mapped ACM into avirtual memory address space, making the ACM available to user-spaceprocesses or the like as virtual memory.

The ACM may be pre-configured to commit its contents upon detection of arestart condition (or other pre-determined triggering event) and, assuch, operations performed on the ACM may be viewed as being “instantlycommitted.” For example, an application may perform a “write-commit”operation on the ACM using memory semantic writes that operate at CPUmemory granularity and speed, without the need for separatecorresponding “commit” commands, which may significantly increase theperformance of applications affected by write-commit latencies. As usedherein, a write-commit operation is an operation in which an applicationwrites data to a memory location (e.g., using a memory semantic access),and then issues a subsequent commit command to commit the operation(e.g., to persistent storage or other commit mechanism).

Applications whose performance is based on write-commit latency, thetime delay between the initial memory write and the subsequentpersistent commit operation, typically attempt to reduce this latency byleveraging a virtual memory system (e.g., using a memory backed file).In this case, the application performs high-performance memory semanticwrite operations in system RAM, but, in order to commit the operations,must perform subsequent “commit” commands to persist each writeoperation to the backing file (or other persistent storage).Accordingly, each write-commit operation may comprise its own separatecommit command. For example, in a database logging application, each logtransaction must be written and committed before a next transaction islogged. Similarly, messaging systems (e.g., store and forward systems)must write and commit each incoming message, before receipt of themessage can be acknowledged. The write-commit latency, therefore,comprises a relatively fast memory semantic write followed by a muchslower operation to commit the data to persistent storage. Write-commitlatency may include several factors including, access times topersistent storage, system call overhead (e.g., translations between RAMaddresses, backing store LBA, etc.), and so on. Examples of applicationsthat may benefit from reduced write-commit latency include, but are notlimited to: database logging applications, filesystem logging, messagingapplications (e.g., store and forward), semaphore primitives, and so on.

The systems, apparatus, and methods for auto-commit memory disclosedherein may be used to significantly increase the performance ofwrite-commit latency bound applications by providing direct access to amemory region at any suitable level of addressing granularity includingbyte level, page level, cache-line level, or other memory region level,that is guaranteed to be committed in the event of a system failure orother restart event, without the application issuing a commit command.Accordingly, the write-commit latency of an application may be reducedto the latency of a memory semantic access (a single write over a systembus).

FIG. 2 is a block diagram of a system 1000 comprising one embodiment ofan auto-commit memory (ACM) 1011. As used herein, an auto-commit memorycomprises low-latency, high reliability memory media, exposed to ACMusers for direct memory semantic access, at a memory semantic access andaddress granularity level of at least byte level, combined with logicand components together configured to restore the same state of datastored in the ACM 1011 that existed prior to the restart event and thesame level of memory semantic access to data stored in the auto-commitmemory after a restart event. In certain embodiments, the ACM 1011guarantees that data stored in the ACM 1011 will be accessible after arestart event. The ACM 1011, in one embodiment, comprises a volatilememory media coupled to a controller, logic, and other components thatcommit data to a non-volatile storage medium when necessary or whendirected by an ACM user. In a further embodiment, the ACM 1011 mayinclude a natively non-volatile storage medium such as phase changememory (PCM or PRAM), and a triggered commit action may process data onthe non-volatile storage medium in response to a restart event such thatthe data remains available to an owner of the data after the restartevent.

Accordingly, when data is written to the ACM 1011, it may not initiallybe “committed” per se (is not necessarily stored on a persistent memorymedia and/or state); rather, a pre-configured process is setup topreserve the ACM data and its state, if a restart event occurs while theACM data is stored in the ACM 1011. The pre-configuring of this restartsurvival process is referred to herein as “arming.” The ACM 1011 may becapable of performing the pre-configured commit action autonomously andwith a high degree of assurance, despite the system 1000 experiencingfailure conditions or another restart event. As such, an entity thatstores data on the ACM 1011 may consider the data to be “instantaneouslycommitted” or safe from loss or corruption, at least as safe as if thedata were stored in a non-volatile storage device such as a hard diskdrive, tape storage media, or the like.

In embodiments where the ACM 1011 comprises a volatile memory media, theACM 1011 may make the volatile memory media appear as a non-volatilememory, may present the volatile memory as a non-volatile medium, or thelike, because the ACM 1011 preserves data, such as ACM data and/or ACMmetadata 1015, across system restart events. The ACM 1011 may allow avolatile memory media to be used as a non-volatile memory media bydetermining that a trigger event, such as a restart or failurecondition, has occurred, copying the contents of the volatile memorymedia to a non-volatile memory media during a hold-up time after thetrigger event, and copying the contents back into the volatile memorymedia from the non-volatile memory media after the trigger event isover, power has been restored, the restart event has completed, or thelike.

In one embodiment, the ACM 1011 is at least byte addressable. A memorymedia of the ACM 1011, in certain embodiments, may be natively byteaddressable, directly providing the ACM 1011 with byte addressability.In another embodiment, a memory media of the ACM 1011 is not nativelybyte addressable, but a volatile memory media of the ACM 1011 isnatively byte addressable, and the ACM 1011 writes or commits thecontents of the byte addressable volatile memory media to the non-byteaddressable memory media of the ACM 1011 in response to a trigger event,so that the volatile memory media renders the ACM 1011 byte addressable.

The ACM 1011 may be accessible to one or more computing devices, such asthe host 1014. As used herein a computing device (such as the host 1014)refers to a computing device capable of accessing an ACM. The host 1014may be a computing device that houses the ACM 1011 as a peripheral; theACM 1011 may be attached to a system bus 1040 of the host 1014; the ACM1011 may be in communication with the host 1014 over a data network;and/or the ACM 1011 may otherwise be in communication with the host1014. The host 1014, in certain embodiments, may access the ACM 1011hosted by another computing device. The access may be implemented usingany suitable communication mechanism, including, but not limited to: CPUprogrammed IO (CPIO), port-mapped IO (PMIO), memory-mapped IO (MMIO), aBlock interface, a PCI-e bus, Infiniband, RDMA, or the like. The host1014 may comprise one or more ACM users 1016. As used herein, an ACMuser 1016 refers to any operating system (OS), virtual operatingplatform (e.g., an OS with a hypervisor), a guest OS, application,process, thread, entity, utility, user, or the like, that is configuredto access the ACM 1011.

The ACM 1011 may be physically located at one or more levels of the host1014. In one embodiment, the ACM 1011 may be connected to a PCI-e busand may be accessible to the host 1014 with MMIO. In another embodiment,the ACM 1011 may be directly accessible to a CPU of the host 1014 via amemory controller. For example, the ACM 1011 may be directly attached toand/or directly (e.g., Quick Path Interconnect (QPI)) in communicationwith a CPU of the host 1014 or the like. Volatile media of the ACM 1011and non-volatile backing media of the ACM 1011, in certain embodiments,may not be physically co-located within the same apparatus, but may bein communication over a communications bus, a data network, or the like.In other embodiments, as described below, hardware components of the ACM1011 may be tightly coupled, and integrated in a single physicalhardware apparatus. Volatile memory media and/or non-volatile memorymedia of the ACM 1011, in one embodiment, may be integrated with, or mayotherwise cooperate with, a CPU cache hierarchy of the host 1014, totake advantage of CPU caching technologies such as write combining orthe like.

One or more ACM buffers 1013, in certain embodiments, may be mapped intoan address range of a physical memory address space addressable by aCPU, a kernel, or the like of the host device 1014, such as the memorysystem 1018 described below. For example, one or more ACM buffers 1013may be mapped as directly attached physical memory, as MMIO addressablephysical memory over a PCI-e bus, or otherwise mapped as one or morepages of physical memory. At least a portion of the physically mappedACM buffers 1013, in a further embodiment, may be mapped into a virtualmemory address space, accessible to user-space processes or the like asvirtual memory.

Allowing ACM users 1016 to directly address the ACM buffers 1013, incertain embodiments, bypasses one or more layers of the traditionaloperating system memory stack of the host device 1014, providing directload/store operation access to kernel-space and/or user-spaceapplications. An operating system, using a kernel module, an applicationprogramming interface, the storage management layer (SML) 1050 describedbelow, or the like, in one embodiment, maps and unmaps ACM buffers 1013to and from the memory system 1018 for one or more ACM users 1016, andthe ACM users 1016 may directly access an ACM buffer 1013 once theoperating system maps the ACM buffer 1013 into the memory system 1018.In a further embodiment, the operating system may also service systemflush calls for the ACM buffers 1013, or the like.

The SML 1050 and/or the SML API 1019 described below, in certainembodiments, provide an interface for ACM users 1016, an operatingsystem, and/or other entities to request certain ACM functions, such asa map function, an unmap function, a flush function, and/or other ACMfunctions. To perform a flush operation in response to a flush request,the ACM 1011 may perform a commit action for each ACM buffer 1013associated with the flush request. Each ACM buffer 1013 is committed asindicated by the ACM metadata 1015 of the associated ACM buffer 1013. Aflush function, in various embodiments, may be specific to one or moreACM buffers 1013, system-wide for all ACM buffers 1013, or the like. Inone embodiment, a CPU, an operating system, or the like for the host1014 may request an ACM flush operation in response to, or as part of aCPU cache flush, a system-wide data flush for the host 1014, or anothergeneral flush operation.

An ACM user 1016, an operating system, or the like may request a flushoperation to maintain data consistency prior to performing a maintenanceoperation, such as a data snapshot or a backup, to commit ACM data priorto reallocating an ACM buffer 1013, to prepare for a scheduled restartevent, or for other circumstances where flushing data from an ACM buffer1013 may be beneficial. An ACM user 1016, an operating system, or thelike, in certain embodiments, may request that the ACM 1011 map and/orunmap one or more ACM buffers 1013 to perform memory management for theACM buffers 1013; to reallocate the ACM buffers 1013 betweenapplications or processes; to allocate ACM buffers 1013 for new data,applications, or processes; to transfer use of the ACM buffers 1013 to adifferent host 1014 (in shared ACM 1011 embodiments); or to otherwisemanipulate the memory mapping of the ACM buffers 1013. In anotherembodiment, the SML 1050 may dynamically allocate, map, and/or unmap ACMbuffers 1013 using a resource management agent as described below.

Since the ACM 1011 is guaranteed to auto-commit the data stored thereonin the event of a trigger event, the host 1014 (or ACM user 1016) mayview data written to the ACM 1011 as being instantaneously “committed”or non-volatile, as the host 1014 or ACM user 1016 may access the databoth before and after the trigger event. Advantageously, while therestart event may cause the ACM user 1016 to be re-started orre-initialized the data stored in the ACM 1011 is in the samestate/condition after the restart event as it was before the restartevent. The host 1014 may, therefore, write to the ACM 1011 using memorywrite semantics (and at CPU speeds and granularity), without the needfor explicit commit commands by relying on the pre-configured trigger ofthe ACM 1011 to commit the data in the event of a restart (or othertrigger event).

The ACM 1011 may comprise a plurality of auto-commit buffers 1013, eachcomprising respective ACM metadata 1015. As discussed below, the ACMmetadata 1015 may include data to facilitate committing of ACM data inresponse to a triggering event for the auto-commit buffer 1013, such asa logical identifier for data in the ACM buffer 1013, an identifier of acommit agent 1020, instructions for a commit process or other processingprocedure, security data, or the like. The auto-commit buffers 1013 maybe of any suitable size, from a single sector, page, byte, or the like,to a virtual or logical page size (e.g., 80 to 400 kb). The size of theauto-commit buffers 1013 may be adapted according to the storagecapacity of the underlying non-volatile storage media, and or hold-uptime available from the secondary power supply 1024.

In one embodiment, the ACM 1011 may advertise or present to the host1014, to ACM users 1016, or the like, a storage capacity of the ACMbuffers 1013 that is larger than an actual storage capacity of memory ofthe ACM buffers 1013. To provide the larger storage capacity, the ACM1011 may dynamically map and unmap ACM buffers 1013 to the memory system1018 and to the non-volatile backing memory of the ACM 1011, such as thenon-volatile memory 110 described above. For example, the ACM 1011 mayprovide virtual address ranges for the ACM buffers 1013, and demand pagedata and/or ACM buffers 1013 to the non-volatile memory 110 as ACMbuffer 1013 accesses necessitate. In another embodiment, for ACM buffers1013 that are armed to commit to one or more predefined LBAs of thenon-volatile memory 110, the ACM 1011 may dynamically move the ACM dataand ACM metadata 1015 from the ACM buffers 1013 to the associated LBAsof the non-volatile memory 110, freeing storage capacity of the ACMbuffers 1013 to provide a larger storage capacity. The ACM 1011 mayfurther return the ACM data and ACM metadata 1015 back to one or moreACM buffers 1013 as ACM buffers become available, certain addressesoutside the data of currently loaded ACM buffers 1013 is requested, orthe like, managing storage capacity of the ACM buffers 1013.

The ACM 1011 is pre-configured or “armed” to implement one or more“triggered commit actions” in response to a restart condition (or other,pre-determined condition). As used herein, a restart condition or eventmay include, but is not limited to a software or hardwareshutdown/restart of a host 1014, a failure in a host 1014 computingdevice, a failure of a component of the host 1014 (e.g., failure of thebus 1040), a software fault (e.g., an fault in software running on thehost 1014 or other computing device), a loss of the primary powerconnection 1030, an invalid shutdown, or another event that may causethe loss of data stored in a volatile memory.

In one embodiment, a restart event comprises the act of the host 1014commencing processing after an event that can cause the loss of datastored within a volatile memory of the host 1014 or a component in thehost 1014. The host 1014 may commence/resume processing once the restartcondition or event has finished, a primary power source is available,and the like.

The ACM 1011 is configured to detect that a restart event/condition hasoccurred and/or respond to a restart event by initiating a recoverystage. During a recovery stage, the ACM 1011 may restore the data of theACM 1011 to the state prior to the restart event. Alternatively, or inaddition, during the recovery stage, the ACM 1011 may completeprocessing of ACM data or ACM metadata 1015 needed to satisfy aguarantee that data in the ACM 1011 is available to ACM users after therestart event. Alternatively, or in addition, during the recovery stage,the ACM 1011 may complete processing of ACM data or ACM metadata 1015needed to satisfy a guarantee that data in the ACM 1011 is committedafter the restart event. As used herein, “commit” means data in the ACM1011 is protected from loss or corruption even after the restart eventand is persisted as required per the arming information associated withthe data. In certain embodiments, the recovery stage includes processingACM data and ACM metadata 1015 such that the ACM data is persisted, eventhough the restart event occurred.

As used herein, a triggered commit action is a pre-configured commitaction that is armed to be performed by the ACM 1011 in response to atriggering event (e.g., a restart event, a flush command, or otherpre-determined event). In certain embodiments, the triggered commitaction persists at least enough ACM data and/or ACM metadata 1015 tomake data of the ACM 1011 available after a system restart, to satisfy aguarantee of the ACM 1011 that the data will be accessible to an ACMuser after a restart event, in certain embodiments, this guarantee issatisfied, at least in part, by committing and/or persisting data of theACM 1011 to non-volatile memory media. A triggered commit action may becompleted before, during, and/or after a restart event. For example, theACM 1011 may write ACM data and ACM metadata 1015 to a predefinedtemporary location in the nonvolatile memory 110 during a hold-up timeafter a restart event, and may copy the ACM data back into the ACMbuffers 1013, to an intended location in the nonvolatile memory 110, orperform other processing once the restart event is complete.

A triggered commit action may be “armed” when the ACM 1011 is requestedand/or a particular ACM buffer 1013 is allocated for use by a host 1014.In some embodiments, an ACM 1011 may be configured to implement atriggered commit action in response to other, non-restart conditions.For example, an operation directed to a particular logical address(e.g., a poke), may trigger the ACM 1011, a flush operation may triggerthe ACM 1011, or the like. This type of triggering may be used to committhe data of the ACM 1011 during normal operation (e.g., non-restart ornon-failure conditions).

The arming may occur when an auto-commit buffer 1013 is mapped into thememory system 1018 of the host 1014. Alternatively, arming may occur asa separate operation. As used herein, arming an auto-commit buffer 1013comprises performing the necessary configuration steps needed tocomplete the triggered action when the action is triggered. Arming mayinclude, for example, providing the ACM metadata 1015 to the ACM 1011 orthe like. In certain embodiments, arming further includes performing thenecessary configuration steps needed to complete a minimal set of stepsfor the triggered action, such that the triggered action is capable ofcompleting after a trigger event. In certain embodiments, arming furtherincludes verifying the arming data (e.g., verifying that the contents ofthe auto-commit buffer 1013, or portion thereof, can be committed asspecified in the ACM metadata 1015) and verifying that the ACM 1011 iscapable and configured to properly perform the triggered action withouterror or interruption.

The verification may ensure that once armed, the ACM 1011 can implementthe triggered commit action when required. If the ACM metadata 1015cannot be verified (e.g., the logical identifier or other ACM metadata1015 is invalid, corrupt, unavailable, or the like), the armingoperation may fail; memory semantic operations on the auto-commit buffer1013 may not be allowed unit the auto-commit buffer 1013 is successfullyarmed with valid ACM metadata 1015. For example, an auto-commit buffer1013 that is backed by a hard disk having a one-to-one mapping betweenLBA and physical address, may fail to arm if the LBA provided for thearming operation does not map to a valid (and operational) physicaladdress on the disk. Verification in this case may comprise querying thedisk to determine whether the LBA has a valid, corresponding physicaladdress and/or using the physical address as the ACM metadata 1015 ofthe auto-commit buffer 1013.

The armed triggered commit actions are implemented in response to theACM 1011 (or other entity) detecting and/or receiving notification of atriggering event, such as a restart condition. In some embodiments, anarmed commit action is a commit action that can be performed by the ACM1011, and that requires no further communication with the host 1014 orother devices external to the “isolation zone” of the ACM 1011(discussed below). Accordingly, the ACM 1011 may be configured toimplement triggered commit actions autonomously of the host 1014 and/orother components thereof. The ACM 1011 may guarantee that triggeredcommit actions can be committed without errors and/or despite externalerror conditions. Accordingly, in some embodiments, the triggered commitactions of the ACM 1011 do not comprise and/or require potentiallyerror-introducing logic, computations, and/or calculations. In someembodiments, a triggered commit action comprises committing data storedon the volatile ACM 1011 to a persistent storage location. In otherembodiments, a triggered commit action may comprise additionalprocessing of committed data, before, during, and/or after a triggeringevent, as described below. The ACM 1011 may implement pre-configuredtriggered commit actions autonomously; the ACM 1011 may be capable ofimplementing triggered commit actions despite failure or restartconditions in the host 1014, loss of primary power, or the like. The ACM1011 can implement triggered commit actions independently due to armingthe ACM 1011 as described above.

The ACM metadata 1015 for an ACM buffer 1013, in certain embodiments,identifies the data of the ACM buffer 1013. For example, the ACMmetadata 1015 may identify an owner of the data, may describe the dataitself, or the like. In one embodiment, an ACM buffer 1013 may havemultiple levels of ACM metadata 1015, for processing by multipleentities or the like. The ACM metadata 1015 may include multiple nestedheaders that may be unpackaged upon restart, and used by variousentities or commit agents 1020 to determine how to process theassociated ACM data to fulfill the triggered commit action as describedabove. For example, the ACM metadata 1015 may include block metadata,file metadata, application level metadata, process execution point orcallback metadata, and/or other levels of metadata. Each level ofmetadata may be associated with a different commit agent 1020, or thelike. In certain embodiments, the ACM metadata 1015 may include securitydata, such as a signature for an owner of the associated ACM data, apre-shared key, a nonce, or the like, which the ACM 1011 may use duringrecovery to verify that a commit agent 1020, an ACM user 1016, or thelike is authorized to access committed ACM metadata 1015 and/orassociated ACM data. In this manner, the ACM 1011 may prevent ownershipspoofing or other unauthorized access. In one embodiment, the ACM 1011does not release ACM metadata 1015 and/or associated ACM data until arequesting commit agent 1020, ACM user 1016, or the like provides validauthentication, such as a matching signature or the like.

One or more commit agents 1020, such as the commit management apparatus1122 described below with regard to FIG. 3, in certain embodiments,process ACM data based on the associated ACM metadata 1015 to execute atriggered commit action. A commit agent 1020, in various embodiments,may comprise software, such as a device driver, a kernel module, the SML1050, a thread, a user space application, or the like, and/or hardware,such as the controller 1004 described below, that is configured tointerpret ACM metadata 1015 and to process the associated ACM dataaccording to the ACM metadata 1015. In embodiments with multiple commitagents 1020, the ACM metadata 1015 may identify one or more commitagents 1020 to process the associated ACM data. The ACM metadata 1015may identify a commit agent 1020, in various embodiments, by identifyinga program/function of the commit agent 1020 to invoke (e.g., a file pathof the program), by including computer executable code of the commitagent 1020 (e.g., binary code or scripts), by including a uniqueidentifier indicating which of a set of registered commit agents 1020 touse, and/or by otherwise indicating a commit agent 1020 associated withcommitted ACM metadata 1015. The ACM metadata 1015, in certainembodiments, may be a functor or envelope which contains theinformation, such as function pointer and bound parameters for a commitagent 1020, to commit the ACM data upon restart recovery.

In one embodiment, a primary commit agent 1020 processes ACM metadata1015, and hands-off or transfers ACM metadata 1015 and/or ACM data toone or more secondary commit agents 1020 identified by the ACM metadata1015. A primary commit agent 1020, in one embodiment, may be integratedwith the ACM 1011, the controller 1004, or the like. An ACM user 1016 orother third party, in certain embodiments, may provide a secondarycommit agent 1020 for ACM data that the ACM user 1016 or other thirdparty owns, and the primary commit agent 1020 may cooperate with theprovided secondary commit agent 1020 to process the ACM data. The one ormore commit agents 1020 for ACM data, in one embodiment, ensure and/orguarantee that the ACM data remains accessible to an owner of the ACMdata after a restart event. As described above with regard to triggeredcommit actions, a commit agent 1020 may process ACM metadata 1015 andassociated ACM data to perform one or more triggered commit actionsbefore, during, and/or after a trigger event, such as a failure or otherrestart event.

In one embodiment, a commit agent 1020, in cooperation with the ACM 1011or the like, may store the ACM metadata 1015 in a persistent ornon-volatile location in response to a restart or other trigger event.The commit agent 1020 may store the ACM metadata 1015 at a knownlocation, may store pointers to the ACM metadata 1015 at a knownlocation, may provide the ACM metadata 1015 to an external agent or datastore, or the like so that the commit agent 1020 may process the ACMmetadata 1015 and associated ACM data once the restart or other triggerevent has completed. The known location may include one or morepredefined logical block addresses or physical addresses of thenon-volatile memory 110, a predefined file, or the like. In certainembodiments, hardware of the ACM 1011 is configured to cooperate towrite the ACM metadata 1015 and/or pointers to the ACM metadata 1015 ata known location. In one embodiment, the known location may be atemporary location that stores the ACM data and ACM metadata 1015 untilthe host 1014 has recovered from a restart event and the commit agent1020 may continue to process the ACM data and ACM metadata 1015. Inanother embodiment, the location may be a persistent location associatedwith the ACM metadata 1015.

In response to completion of a restart event or other trigger event,during recovery, in one embodiment, a commit agent 1020 may locate andretrieve the ACM metadata 1015 from the non-volatile memory 110, from apredefined location or the like. The commit agent 1020, in response tolocating and retrieving the ACM metadata 1015, locates the ACM dataassociated with the retrieved ACM metadata 1015. The commit agent 1020,in certain embodiments, may locate the ACM data in a substantiallysimilar manner as the commit agent 1020 locates the ACM metadata 1015,retrieving ACM data from a predefined location, retrieving pointers tothe ACM data from a predefined location, receiving the ACM data from anexternal agent or data store, or the like. In one embodiment, the ACMmetadata 1015 identifies the associated ACM data and the commit agent1020 uses the ACM metadata 1015 to locate and retrieve the associatedACM data. For example, the commit agent 1020 may use a predefinedmapping to associate ACM data with ACM metadata 1015 (e.g the Nth pieceof ACM data may be associated with the Nth piece of ACM metadata 1015 orthe like), the ACM metadata 1015 may include a pointer or index for theassociated ACM data, or another predefined relationship may existbetween committed ACM metadata 1015 and associated ACM data. In anotherembodiment, an external agent may indicate to the commit agent 1020where associated ACM data is located.

In response to locating and retrieving the ACM metadata 1015 andassociated ACM data, the commit agent 1020 interprets the ACM metadata1015 and processes the associated ACM data based on the ACM metadata1015. For example, in one embodiment, the ACM metadata 1015 may identifya block storage volume and LBA(s) where the commit agent 1020 is towrite the ACM data upon recovery. In another embodiment, the ACMmetadata 1015 may identify an offset within a file within a file systemwhere the commit agent 1020 is to write the ACM data upon recovery. In afurther embodiment, the ACM metadata 1015 may identify an applicationspecific persistent object where the commit agent 1020 is to place theACM data upon recovery, such as a database record or the like. The ACMmetadata 1015, in an additional embodiment, may indicate a procedure forthe commit agent 1020 to call to process the ACM data, such as a delayedprocedure call or the like. In an embodiment where the ACM 1011advertises or presents volatile ACM buffers 1013 as nonvolatile memory,the ACM metadata 1013 may identify an ACM buffer 1013 where the commitagent 1020 is to write the ACM data upon recovery.

In certain embodiments, the ACM metadata 1015 may identify one or moresecondary commit agents 1020 to further process the ACM metadata 1015and/or associated ACM data. A secondary commit agent 1020 may processACM metadata 1015 and associated ACM data in a substantially similarmanner to the commit agent 1020 described above. Each commit agent 1020may process ACM data in accordance with a different level or subset ofthe ACM metadata 1015, or the like. The ACM metadata 1015 may identify asecondary commit agent 1020, in various embodiments, by identifying aprogram/function of the secondary commit agent 1020 to invoke (e.g., afile path of the program), by including computer executable code of thesecondary commit agent 1020, by including a unique identifier indicatingwhich of a set of registered secondary commit agents 1020 to use, and/orby otherwise indicating a secondary commit agent 1020 associated withcommitted ACM metadata 1015.

In one embodiment, a secondary commit agent 1020 processes a remainingportion of the ACM metadata 1015 and/or of the ACM data after a previouscommit agent 1020 has processed the ACM metadata 1015 and/or the ACMdata. In a further embodiment, the ACM metadata 1015 may identifyanother non-volatile medium separate from the ACM 1011 for the secondarycommit agent 1020 to persist the ACM data even after a host experiencesa restart event. By committing the ACM metadata 1015 and the associatedACM data from the ACM buffers 1013 in response to a trigger event, suchas a failure or other restart condition, and processing the ACM metadata1015 and the associated ACM data once the trigger event has completed orrecovered, the ACM 1011 may guarantee persistence of the ACM data and/orperformance of the triggered commit action(s) defined by the ACMmetadata 1015.

The ACM 1011 is communicatively coupled to a host 1014, which, like thehost 114 described above, may comprise operating systems, virtualmachines, applications, a processor complex 1012, a central processingunit 1012 (CPU), and the like. In the FIG. 2 example, these entities arereferred to generally as ACM users 1016. Accordingly, as used herein, anACM user may refer to an operating system, a virtual machine operatingsystem (e.g., hypervisor), an application, a library, a CPUfetch-execute algorithm, or other program or process. The ACM 1011 maybe communicatively coupled to the host 1014 (as well as the ACM users1016) via a bus 1040, such as a system bus, a processor's memoryexchange bus, or the like (e.g., HyperTransport, QuickPath Interconnect(QPI), PCI bus, PCI-e bus, or the like). In some embodiments, the bus1040 comprises the primary power connection 1030 (e.g., the non-volatilestorage device 1102 may be powered through the bus 1040). Although someembodiments described herein comprise solid-state storage devices, suchas certain embodiments of the non-volatile storage device 1102, thedisclosure is not limited in this regard, and could be adapted to useany suitable recording/memory/storage device 1102 and/orrecording/memory/storage media 1110.

The ACM 1011 may be tightly coupled to the device used to perform thetriggered commit actions. For example, the ACM 1011 may be implementedon the same device, peripheral, card, or within the same “isolationzone” as the controller 1004 and/or secondary power source 1024. Thetight coupling of the ACM 1011 to the components used to implement thetriggered commit actions defines an “isolation zone,” which may providean acceptable level of assurance (based on industry standards or othermetric) that the ACM 1011 is capable of implementing the triggeredauto-commit actions in the event of a restart condition. In the FIG. 2example, the isolation zone of the ACM 1011 is provided by the tightcoupling of the ACM 1011 with the autonomous controller 1004 andsecondary power supply 1024 (discussed below).

The controller 1004 may comprise an I/O controller, such as a networkcontroller (e.g., a network interface controller), storage controller,dedicated restart condition controller, or the like. The controller 1004may comprise firmware, hardware, a combination of firmware and hardware,or the like. In the FIG. 2 example, the controller 1004 comprises astorage controller, such as the storage controller 104 and/ornon-volatile storage device controller described above. The controller1004 may be configured to operate independently of the host 1014. Assuch, the controller 1004 may be used to implement the triggered commitaction(s) of the ACM 1011 despite the restart conditions discussedabove, such as failures in the host 1014 (and/or ACM users 1016) and/orloss of the primary power connection 1030.

The ACM 1011 is powered by a primary power connection 1030, which, likethe primary power connection 130 described above, may be provided by asystem bus (bus 1040), external power supply, the host 1014, or thelike. In certain embodiments, the ACM 1011 also includes and/or iscoupled to a secondary power source 1024. The secondary power source1024 may power the ACM 1011 in the event of a failure to the primarypower connection 1030. The secondary power source 1024 may be capable ofproviding at least enough power to enable the ACM 1011 and/or controller1004 to autonomously implement at least a portion of a pre-configuredtriggered commit action(s) when the primary power connection 1030 hasfailed. The ACM 1011, in one embodiment, commits or persists at leastenough data (e.g., ACM data and ACM metadata 1015) while receiving powerfrom the secondary power source 1024, to allow access to the data oncethe primary power connection 1030 has been restored. In certainembodiments, as described above, the ACM 1011 may perform at least aportion of the pre-configured triggered commit action(s) after theprimary power connection 1030 has been restored, using one or morecommit agents 1020 or the like.

The ACM 1011 may comprise volatile memory storage. In the FIG. 2example, the ACM 1011 includes one or more auto-commit buffers 1013. Theauto-commit buffers 1013 may be implemented using a volatile RandomAccess Memory (RAM). In some embodiments, the auto-commit buffers 1013may be embodied as independent components of the ACM 1011 (e.g., inseparate RAM modules). Alternatively, the auto-commit buffers 1013 maybe implemented on embedded volatile memory (e.g., BRAM) available withinthe controller 1004, a processor complex 1012, an FPGA, or othercomponent of the ACM 1011.

Each of the auto-commit buffers 1013 may be pre-configured (armed) witha respective triggered commit action. In some embodiments, eachauto-commit buffer 1013 may comprise its own, respective ACM metadata1015. The ACM metadata 1015, in some embodiments, identifies how and/orwhere the data stored on the auto-commit buffer 1013 is to be committed.In some examples, the ACM metadata 1015 may comprise a logicalidentifier (e.g., an object identifier, logical block address (LBA),file name, or the like) associated with the data in the auto-commitbuffer 1013. The logical identifier may be predefined. In oneembodiment, when an auto-commit buffer 1013 is committed, the datatherein may be committed with the ACM metadata 1015 (e.g., the data maybe stored at a physical storage location corresponding to the logicalidentifier and/or in association with the logical identifier). Tofacilitate committing of ACM data during a hold-up time after a restartevent, the ACM 1011 may write ACM data and ACM metadata 1015 in a singleatomic operation, such as a single page write or the like. To permitwriting of ACM and ACM metadata 1015 in a single atomic operation, theACM buffers 1013 may be sized to correspond to a single write unit for anon-volatile storage media that is used by the ACM 1011. In someembodiments, the ACM metadata 1015 may comprise a network address, anLBA, or another identifier of a commit location for the data.

In a further embodiment, a logical identifier may associate data of anauto-commit buffer 1013 with an owner of the data, so that the data andthe owner maintain the ownership relationship after a restart event. Forexample, the logical identifier may identify an application, anapplication type, a process ID, an ACM user 1016, or another entity of ahost device 1014, so that the ACM data is persistently associated withthe identified entity. In one embodiment, a logical identifier may be amember of an existing namespace, such as a file system namespace, a usernamespace, a process namespace, or the like. In other embodiments, alogical identifier may be a member of a new or separate namespace, suchas an ACM namespace. For example, a globally unique identifiernamespace, as is typically used in distributed systems for identifyingcommunicating entities, may be used as an ACM namespace for logicalidentifiers. The ACM 1011 may process committed ACM data according to alogical identifier for the data once a restart event has completed. Forexample, the ACM 1011 may commit the ACM data to a logical identifierassociated with a temporary location in response to a restart event, andmay write the ACM data to a persistent location identified by anotherlogical identifier during recovery after the restart event.

As described above, the ACM 1011 may be tightly coupled with thecomponents used to implement the triggered commit actions (e.g., the ACM1011 is implemented within an “isolation zone”), which ensures that thedata on the ACM 1011 will be committed in the event of a restartcondition. As used herein, a “tight coupling” refers to a configurationwherein the components used to implement the triggered commit actions ofthe ACM 1011 are within the same “isolation zone,” or two or moredistinct trusted “isolation zones,” and are configured to operatedespite external failure or restart conditions, such as the loss ofpower, invalid shutdown, host 1014 failures, or the like. FIG. 2illustrates a tight coupling between the ACM 1011, the auto-commitbuffers 1013, the controller 1004, which is configured to operateindependently of the host 1014, and the secondary power source 1024,which is configured to power the controller 1004 and the ACM 1011(including the auto-commit buffers 1013) while the triggered commitactions are completed. Examples of a tight coupling include but are notlimited to including the controller 1004, the secondary power source1024, and the auto-commit buffers 1013 on a single printed circuit board(PCB), within a separate peripheral in electronic communication with thehost 1014, and the like. In other embodiments, the ACM 1011 may betightly coupled to other a different set of components (e.g., redundanthost devices, redundant communication buses, redundant controllers,alternative power supplies, and so on).

The ACM 1011 may be accessible by the host 1014 and/or ACM users 1016running thereon. Access to the ACM 1011 may be provided using memoryaccess semantics, such as CPU load/store commands, DMA commands, 3rdparty DMA commands, RDMA commands, atomic test and set commands,manipulatable memory pointers, and so on. In some embodiments, memorysemantic access to the ACM 1011 is implemented over the bus 1040 (e.g.,using a PCI-e BAR as described below).

In a memory semantic paradigm, ACM users 1016 running on the host 1014may access the ACM 1011 via a memory system 1018 of the host 1014. Thememory system 1018 may comprise a memory management unit, virtual memorysystem, virtual memory manager, virtual memory subsystem (or similarmemory address space) implemented by an operating system, avirtualization system (e.g., hypervisor), an application, or the like. Aportion of the ACM 1011 (e.g., one or more auto-commit buffers 1013) maybe mapped into the memory system 1018, such that memory semanticoperations implemented within the mapped memory address range (ACMaddress range 1021) are performed on the ACM 1011.

The SML 1050, in certain embodiments, allocates and/or arbitrates thestorage capacity of the ACM 1011 between multiple ACM users 1016, usinga resource management agent or the like. The resource management agentof the SML 1050 may comprise a kernel module provided to an operatingsystem of the host device 1014, a device driver, a thread, a user spaceapplication, or the like. In one embodiment, the resource managementagent determines how much storage capacity of the ACM buffers 1013 toallocate to an ACM user 1016 and how long the allocation is to last.Because, in certain embodiments, the ACM 1011 commits or persists dataacross restart events, the resource management agent may allocatestorage capacity of ACM buffers 1013 across restart events.

The resource management agent may assign different ACM buffers 1013 todifferent ACM users 1016, such as different kernel and/or user spaceapplications. The resource management agent may allocate ACM buffers1013 to different usage types, may map ACM buffers 1013 to differentnon-volatile memory 110 locations for destaging, or the like. In oneembodiment, the resource management agent may allocate the ACM buffers1013 based on commit agents 1020 associated with the ACM buffers 1013 bythe ACM metadata 1015 or the like. For example, a master commit agent1020 may maintain an allocation map in ACM metadata 1015 identifyingallocation information for ACM buffers 1013 of the ACM 1011 andidentifying, in one embodiment, one or more secondary commit agents1020, and the master commit agent 1020 may allocate a portion of the ACMbuffers 1013 to each of the secondary commit agents 1020. In anotherembodiment, commit agents 1020 may register with the resource managementagent, may request resources such as ACM buffers 1013 from the resourcemanagement agent, or the like. The resource management agent may use apredefined memory management policy, such as a memory pressure policy orthe like, to allocate and arbitrate ACM buffer 1013 storage capacitybetween ACM users 1016.

In some embodiments, establishing an association between an ACM addressrange 1021 within the memory system 1018 and the ACM 1011 may comprisepre-configuring (arming) the corresponding auto-commit buffer(s) 1013with a triggered commit action. As described above, thispre-configuration may comprise associating the auto-commit buffer 1013with a logical identifier or other metadata, which may be stored in theACM metadata 1015 of the buffer 1013. As described above, the ACM 1011may be configured to commit the buffer data to the specified logicalidentifier in the event of a restart condition, or to perform otherprocessing in accordance with the ACM metadata 1015.

Memory semantic access to the ACM 1011 may be implemented using anysuitable address and/or device association mechanism. In someembodiments, memory semantic access is implemented by mapping one ormore auto-commit buffers 1013 of the ACM 1011 into the memory system1018 of the host 1014. In some embodiments, this mapping may beimplemented using the bus 1040. For example, the bus 1040 may comprise aPCI-e (or similar) communication bus, and the mapping may compriseassociating a Base Address Register (BAR) of an auto-commit buffer 1013of the ACM 1011 on the bus 1040 with the ACM address range 1021 in thememory system 1018 (e.g., the host 1014 mapping a BAR into the memorysystem 1018).

The association may be implemented by an ACM user 1016 (e.g., by avirtual memory system of an operating system or the like), through anAPI of a storage layer, such as the storage management layer (SML) 1050.The SML 1050 may be configured to provide access to the auto-commitmemory 1011 to ACM users 1016. The storage management layer 1050 maycomprise a driver, kernel-level application, user-level application,library, or the like. One example of an SML is the Virtual StorageLayer® of Fusion-io, Inc. of Salt Lake City, Utah. The SML 1050 mayprovide a SML API 1019 comprising, inter alia, an API for mappingportions of the auto-commit memory 1011 into the memory system 1018 ofthe host 1014, for unmapping portions of the auto-commit memory 1011from the memory system 1018 of the host 1014, for flushing the ACMbuffers 1013, and the like. The SML 1050 may be configured to maintainmetadata 1051, which may include a forward index 1053 comprisingassociations between logical identifiers of a logical address space andphysical storage locations on the auto-commit memory 1011 and/orpersistent storage media. In some embodiments, ACM 1011 may beassociated with one or more virtual ranges that map to different addressranges of a BAR (or other addressing mechanism). The virtual ranges maybe accessed (e.g., mapped) by different ACM users 1016. Mapping orexposing a PCI-e ACM BAR to the host memory 1018 may be enabled ondemand by way of a SML API 1019 call.

The SML API 1019 may comprise interfaces for mapping an auto-commitbuffer 1013 into the memory system 1018. In some embodiments, the SMLAPI 1019 may extend existing memory management interfaces, such asmalloc, calloc, or the like, to map auto-commit buffers 1013 into thevirtual memory range of ACM user applications 1016 (e.g., a malloc callthrough the SML API 1019 may map one or more auto-commit buffers 1013into the memory system 1018). Alternatively, or in addition, the SML API1019 may comprise one or more explicit auto-commit mapping functions,such as “ACM_alloc,” “ACM_free,” or the like. Mapping an auto-commitbuffer 1013 may further comprise configuring a memory system 1018 of thehost to ensure that memory operations are implemented directly on theauto-commit buffer 1013 (e.g., prevent caching memory operations withina mapped ACM address range 1021).

The association between the ACM address range 1021 within the hostmemory system 1018 and the ACM 1011 may be such that memory semanticoperations performed within a mapped ACM address range 1021 areimplemented directly on the ACM 1011 (without intervening system RAM, orother intermediate memory, in a typical write commit operation,additional layers of system calls, or the like). For example, a memorysemantic write operation implemented within the ACM address range 1021may cause data to be written to the ACM 1011 (on one or more of theauto-commit buffers 1013). Accordingly, in some embodiments, mapping theACM address range 1021 may comprise disabling caching of memoryoperations within the ACM address range 1021, such that memoryoperations are performed on an ACM 1011 and are not cached by the host(e.g., cached in a CPU cache, in host volatile memory, or the like).Disabling caching within the ACM address range 1021 may comprise settinga “non-cacheable” flag attribute associated with the ACM range 1021,when the ACM range 1021 is defined.

As discussed above, establishing an association between the host memorysystem 1018 and the ACM 1011 may comprise “arming” the ACM 1011 toimplement a pre-determined triggered commit action. The arming maycomprise providing the ACM 1011 with a logical identifier (e.g., alogical block address, a file name, a network address, a stripe ormirroring pattern, or the like). The ACM 1011 may use the logicalidentifier to arm the triggered commit action. For example, the ACM 1011may be triggered to commit data to a persistent storage medium using thelogical identifier (e.g., the data may be stored at a physical addresscorresponding to the logical identifier and/or the logical identifiermay be stored with the data in a log-based data structure). Arming theACM 1011 allows the host 1014 to view subsequent operations performedwithin the ACM address range 1021 (and on the ACM 1011) as being“instantly committed,” enabling memory semantic write granularity (e.g.,byte level operations) and speed with instant commit semantics.

Memory semantic writes such as a “store” operation for a CPU aretypically synchronous operations such that the CPU completes theoperation before handling a subsequent operation. Accordingly, memorysemantic write operations performed in the ACM memory range 1021 can beviewed as “instantly committed,” obviating the need for a corresponding“commit” operation in the write-commit operation, which maysignificantly increase the performance of ACM users 1016 affected bywrite-commit latency. The memory semantic operations performed withinthe ACM memory range 1021 may be synchronous. Accordingly, ACM 1011 maybe configured to prevent the memory semantic operations from blocking(e.g., waiting for an acknowledgement from other layers, such as the bus1040, or the like). Moreover, the association between ACM address range1021 and the ACM 1011 allow memory semantic operations to bypass systemcalls (e.g., separate write and commit commands and their correspondingsystem calls) that are typically included in write-commit operations.

Data transfer between the host 1014 and the ACM 1011 may be implementedusing any suitable data transfer mechanism including, but not limitedto: the host 1014 performing processor IO operations (PIO) with the ACM1011 via the bus 1040; the ACM 1011 (or other device) providing one ormore DMA engines or agents (data movers) to transfer data between thehost 1014 and the ACM 1011; the host 1014 performing processor cachewrite/flush operations; or the like.

As discussed above, an ACM may be configured to automatically perform apre-configured triggered commit action in response to detecting certainconditions (e.g., restart or failure conditions). In some embodiments,the triggered commit action may comprise committing data stored on theACM 1014 to a persistent storage media. Accordingly, in someembodiments, an ACM, such as the ACM 1011 described above, may becomprise persistent storage media. FIG. 3 is a block diagram of a system1100 depicting an embodiment of an ACM configured to implement triggeredcommit actions, which may include committing data to a persistent,solid-state, and/or non-volatile storage.

The ACM 1111 of the FIG. 3 example may be tightly coupled to thenon-volatile storage device 1102, which comprises a controller 1104. Thecontroller 1104 may comprise a write data pipeline 1106 and a read datapipeline 1108, which may operate as described above. The non-volatilestorage device 1102 may be capable of persisting data on a non-volatilememory 1110, such as solid-state storage media.

A commit management apparatus 1122 is used to commit data to thenon-volatile memory 1110 in response to a trigger event, such as loss ofprimary power connection, or other pre-determined trigger event.Accordingly, the commit management apparatus 1122 may comprise and/or beconfigured to perform the functions of the auto-commit memory 1011described above. The commit management apparatus 1122 may be furtherconfigured to commit data on the ACM 1111 (e.g., the contents of theauto-commit buffers 1013) to the non-volatile memory 1110 in response toa restart condition (or on request from the host 1014 and/or ACM users1016) and in accordance with the ACM metadata 1015. The commitmanagement apparatus 1122 is one embodiment of a commit agent 1020.

The data on the ACM 1111 may be committed to the persistent storage 1110in accordance with the ACM metadata 1015, such as a logical identifieror the like. The ACM 1111 may commit the data to a temporary locationfor further processing after a restart event, may commit the data to afinal intended location, or the like as, described above. If thenon-volatile memory 1110 is sequential storage device, committing thedata may comprise storing the logical identifier or other ACM metadata1015 with the contents of the auto-commit buffer 1013 (e.g., in a packetor container header). If the non-volatile memory 1110 comprises a harddisk having a 1:1 mapping between logical identifier and physicaladdress, the contents of the auto-commit buffer 1013 may be committed tothe storage location to which the logical identifier maps. Since thelogical identifier or other ACM metadata 1015 associated with the datais pre-configured (e.g., armed), the ACM 1111 implements the triggeredcommit action independently of the host 1014. The secondary power supply1024 supplies power to the volatile auto-commit buffers 1013 of the ACM1111 until the triggered commit actions are completed (and/or confirmedto be completed), or until the triggered commit actions are performed toa point at which the ACM 1111 may complete the triggered commit actionsduring recovery after a restart event.

In some embodiments, the ACM 1111 commits data in a way that maintainsan association between the data and its corresponding logical identifier(per the ACM metadata 1015). If the non-volatile memory 1110 comprises ahard disk, the data may be committed to a storage location correspondingto the logical identifier, which may be outside of the isolation zone1301 (e.g., using a logical identifier to physical address conversion).In other embodiments in which the non-volatile memory 1110 comprises asequential media, such as solid-state storage media, the data may bestored sequentially and/or in a log-based format as described in aboveand/or in U.S. Provisional Patent Application Publication No.61/373,271, entitled “APPARATUS, SYSTEM, AND METHOD FOR CACHING DATA,”and filed 12 Aug. 2010, which is hereby incorporated by reference in itsentirety. The sequential storage operation may comprise storing thecontents of an auto-commit buffer 1013 with a corresponding logicalidentifier (as indicated by the ACM metadata 1015). In one embodiment,the data of the auto-commit buffer 1013 and the corresponding logicalidentifier are stored together on the media according to a predeterminedpattern. In certain embodiments, the logical identifier is stored beforethe contents of the auto-commit buffer 1013. The logical identifier maybe included in a header of a packet comprising the data, or in anothersequential and/or log-based format. The association between the data andlogical identifier may allow a data index to be reconstructed asdescribed above.

As described above, the auto-commit buffers 1013 of the ACM 1011 may bemapped into the memory system 1018 of the host 1014, enabling the ACMusers 1016 of access these buffers 1013 using memory access semantics.In some embodiments, the mappings between logical identifiers andauto-commit buffers 1013 may leverage a virtual memory system of thehost 1014.

For example, an address range within the memory system 1018 may beassociated with a “memory mapped file.” As discussed above, a memorymapped file is a virtual memory abstraction in which a file, portion ofa file, or block device is mapped into the memory system 1018 addressspace for more efficient memory semantic operations on data of thenon-volatile storage device 1102. An auto-commit buffer 1013 may bemapped into the host memory system 1018 using a similar abstraction. TheACM memory range 1021 may, therefore, be represented by a memory mappedfile. The backing file must be stored on the non-volatile memory 1110within the isolation zone 1301 (See FIG. 5 below) or another networkattached non-volatile storage device 1102 also protected by an isolationzone 1301. The auto-commit buffers 1013 may correspond to only a portionof the file (the file itself may be very large, exceeding the capacityof the auto-commit buffers 1013 and/or the non-volatile memory 1110).When a portion of a file is mapped to an auto-commit buffer 1013, theACM user 1016 (or other entity) may identify a desired offset within thefile and the range of blocks in the file that will operate with ACMcharacteristics (e.g., have ACM semantics). This offset will have apredefined logical identifier and the logical identifier and range maybe used to trigger committing the auto-commit buffer(s) 1013 mappedwithin the file. Alternatively, a separate offset for a block (or rangeof blocks) into the file may serve as a trigger for committing theauto-commit buffer(s) 1013 mapped to the file. For example, anytime amemory operation (load, store, poke, etc.) is performed on data in theseparate offset or range of blocks may result in a trigger event thatcauses the auto-commit buffer(s) 1013 mapped to the file to becommitted.

The underlying logical identifier may change, however (e.g., due tochanges to other portions of the file, file size changes, etc.). When achange occurs, the SML 1050 (via the SML API 1019, an ACM user 1016, orother entity) may update the ACM metadata 1015 of the correspondingauto-commit buffers 1013. In some embodiments, the SML 1050 may beconfigured to query the host 1014 (operating system, hypervisor, orother application) for updates to the logical identifier of filesassociated with auto-commit buffers 1013. The queries may be initiatedby the SML API 1019 and/or may be provided as a hook (callbackmechanism) into the host 1014. When the ACM user 1016 no longer needsthe auto-commit buffer 1013, the SML 1050 may de-allocate the buffer1013 as described above. De-allocation may further comprise informingthe host 1014 that updates to the logical identifier are no longerneeded.

In some embodiments, a file may be mapped across multiple storagedevices (e.g., the storage devices may be formed into a RAID group, maycomprise a virtual storage device, or the like). Associations betweenauto-commit buffers 1013 and the file may be updated to reflect the filemapping. This allows the auto-commit buffers 1013 to commit the data tothe proper storage device. The ACM metadata 1015 of the auto-commitbuffers 1013 may be updated in response to changes to the underlyingfile mapping and/or partitioning as described above. Alternatively, thefile may be “locked” to a particular mapping or partition while theauto-commit buffers 1013 are in use. For example, if aremapping/repartitioning of a file is required, the correspondingauto-commit buffers 1013 may commit data to the file, and then bere-associated with the file under the new mapping/partitioning scheme.The SML API 1019 may comprise interfaces and/or commands for using theSML 1050 to lock a file, release a file, and/or update ACM metadata 1015in accordance with changes to a file.

Committing the data to solid-state, non-volatile storage 1110 maycomprise the storage controller 1104 accessing data from the ACM 1111auto-commit buffers 1013, associating the data with the correspondinglogical identifier (e.g., labeling the data), and injecting the labeleddata into the write data pipeline 1106 as described above. In someembodiments, to ensure there is a page program command capable ofpersisting the ACM data, the storage controller 1104 maintains two ormore pending page programs during operation. The ACM data may becommitted to the non-volatile memory 1110 before writing the power lossidentifier (power-cut fill pattern) described above.

FIG. 4 depicts one embodiment of a system 1200 comprising a plurality ofauto-commit memories. In the FIG. 4 example, memory semantic accessesimplemented by the host 1014 may be stored on a plurality of ACMs,including 1011A and 1011B. In some embodiments, host data may bemirrored between the ACMs 1011A and 1011B. The mirroring may beimplemented using a multi-cast bus 1040. Alternatively, or in addition,one of the ACMs (AM 1011A) may be configured to rebroadcast data to theACM 1011B. The ACMs 1011A and 1011B may be local to one another (e.g.,on the same local bus). Alternatively, the ACMs 1011A and 1011B maylocated on different systems, and may be communicatively coupled via abus that supports remove data access, such as Infiniband, a remote PCIbus, RDMA, or the like.

In some embodiments, the ACMs 1011A and 1011B may implement a stripingscheme (e.g., a RAID scheme). In this case, different portions of thehost data may be sent to different ACMs 1011A and/or 1011B. Driver levelsoftware, such as a volume manager implemented by the SML 1050 and/oroperating system 1018 may map host data to the proper ACM per thestriping pattern.

In some configurations, the memory access semantics provided by the ACMsmay be adapted according to a particular storage striping pattern. Forexample, if host data is mirrored from the ACM 1011A to the ACM 1011B, amemory semantic write may not complete (and/or an acknowledgement maynot be returned) until the ACM 1011A verifies that the data was sent tothe ACM 1011B (under the “instant commit” semantic). Similar adaptationsmay be implemented when ACMs are used in a striping pattern (e.g., amemory semantic write may be not return and/or be acknowledged, untilthe striping pattern for a particular operation is complete). Forexample, in a copy on write operation, the ACM 1011A may store the dataof an auto-commit buffer, and then cause the data to be copied to theACM 1011B. The ACM 1011A may not return an acknowledgment for the writeoperation (or allow the data to be read) until the data is copied to theACM 1011B.

The use of mirrored ACM devices 1011A and 1011B may be used in ahigh-availability configuration. For example, the ACM devices 1011A and1011B may be implemented in separate host computing devices. Memorysemantic accesses to the devices 1011A and 1011B are mirrored betweenthe devices as described above (e.g., using PCI-e access). The devicesmay be configured to operate in high-availability mode, such that deviceproxying may not be required. Accordingly, trigger operations (as wellas other memory semantic accesses) may be mirrored across both devices1011A and 1011B, but the devices 1011A and 1011B may not have to waitfor a “acknowledge” from the other before proceeding, which removes theother device from the write-commit latency path.

FIG. 5 is a block diagram of a one embodiment 1300 of a commitmanagement apparatus 1122. The commit management apparatus 1122 may betightly coupled (e.g., within an isolation zone 1301) to the auto-commitmemory 1011, the non-volatile storage controller 1304, the non-volatilestorage media 1310, and/or the secondary power supply 1324. The tightcoupling may comprise implementing these components 132, 1011, 1304,1310, and/or 1324 on the same die, the same peripheral device, on thesame card (e.g., the same PCB), within a pre-defined isolation zone, orthe like. The tight coupling may ensure that the triggered commitactions of the ACM buffers 1013 are committed in the event of a restartcondition.

The commit management apparatus 1122 includes a monitor module 1310,which may be configured to detect restart conditions, such as power lossor the like. The monitor module 1310 may be configured to sensetriggering events, such as restart conditions (e.g., shutdown, restart,power failures, communication failures, host or application failures,and so on) and, in response, to initiate the commit module 1320 toinitiate the commit loss mode of the apparatus 1122 (failure loss mode)and/or to trigger the operations of other modules, such as modules 1312,1314, 1316, 1317, and/or 1318. The commit module 1320 includes anidentification module 1312, terminate module 1314, corruption module1316, and completion module 1318, which may operate as described above.

The identification module 1312 may be further configured to identifytriggered commit actions to be performed for each ACM buffer 1013 of theACM 1011. As discussed above, the identification module 1312 mayprioritize operations based on relative importance, with acknowledgedoperations being given a higher priority than non-acknowledgedoperations. The contents of auto-commit buffers 1013 that are armed tobe committed may be assigned a high priority due to the “instant commit”semantics supported thereby. In some embodiments, the ACM triggeredcommit actions may be given a higher priority than the acknowledgedcontents of the write data pipeline 1306. Alternatively, the contents ofarmed auto-commit buffers 1013 may be assigned the “next-highest’priority. The priority assignment may be user configurable (via an API,IO control (IOCTL), or the like).

The termination module 1314 terminates non-essential operations to allow“essential” to continue as described above. The termination module 1314may be configured to hold up portions of the ACM 1011 that are “armed”to be committed (e.g., armed auto-commit buffers), and may terminatepower to non-armed (unused) portions of the auto-commit memory 1011. Thetermination module 1314 may be further configured to terminate power toportions of the ACM 1011 (individual auto-commit buffers 1013) as thecontents of those buffers are committed.

The corruption module 1316 identifies corrupt (or potentially corrupt)data in the write data pipeline 1306 as described above. The module 1316may be further configured to identify corrupt ACM data 1011 (data thatwas written to the ACM 1011 during a power disturbance or other restartcondition). The corruption module 1316 may be configured to preventcorrupt data on the ACM 1011 from being committed in a triggered commitaction.

An ACM module 1317 is configured to access armed auto-commit buffers inthe auto-commit memory 1011, identify the ACM metadata 1015 associatedtherewith (e.g., label the data with the corresponding logicalidentifier per the ACM metadata 1015), and inject the data (andmetadata) into the write data pipeline of the non-volatile storagecontroller 1304. In some embodiments, the logical identifier (or otherACM metadata 1015) of the auto-commit buffer 1013 may be stored in thebuffer 1013 itself. In this case, the contents of the auto-commit buffer1013 may be streamed directly into a sequential and/or log-based storagedevice without first identifying and/or labeling the data. The ACMmodule 1317 may inject data before or after data currently in the writedata pipeline 1306. In some embodiments, data committed from the ACM1011 is used to “fill out” the remainder of a write buffer of the writedata pipeline 1306 (after removing potentially corrupt data). If theremaining capacity of the write buffer is insufficient, the write bufferis written to the non-volatile storage 1310, and a next write buffer isfilled with the remaining ACM data.

As discussed above, in some embodiments, the non-volatile storagecontroller 1304 may maintain an armed write operation (logical pagewrite) to store the contents of the write data pipeline 1306 in theevent of power loss. When used with an ACM 1011, two (or more) armedwrite operations (logical page writes) may be maintained to ensure thecontents of both the write data pipeline 1306, and all the armed buffers1013 of the ACM 1011 can be committed in the event of a restartcondition. Because a logical page in a write buffer may be partiallyfilled when a trigger event occurs, the write buffer is sized to hold atleast one more logical page of data than the total of all the datastored in all ACM buffers 1013 of the ACM 1011 and the capacity of datain the write data pipeline that has been acknowledged as persisted. Inthis manner, there will be sufficient capacity in the write buffer tocomplete the persistence of the ACM 1011 in response to a trigger event.Accordingly, the auto-commit buffers 1013 may be sized according to theamount of data the ACM 1011 is capable of committing. Once thisthreshold is met, the SML 1050 may reject requests to use ACM buffers1013 until more become available.

The completion module 1318 is configured to flush the write datapipeline regardless of whether the certain buffers, packets, and/orpages are completely filled. The completion module 1318 is configured toperform the flush (and insert the related padding data) after data onthe ACM 1011 (if any) has been injected into the write data pipeline1306. The completion module 1318 may be further configured to injectcompletion indicator into the write data pipeline, which may be used toindicate that a restart condition occurred (e.g., a restart conditionfill pattern). This fill pattern may be included in the write datapipeline 1306 after injecting the triggered data from the ACM 1011.

As discussed above, the secondary power supply 1324 may be configured toprovide sufficient power to store the contents of the ACM 1011 as wellas data in the write data pipeline 1306. Storing this data may compriseone or more write operations (e.g., page program operations), in whichdata is persistently stored on the non-volatile storage media 1310. Inthe event a write operation fails, another write operation, on adifferent storage location, may be attempted. The attempts may continueuntil the data is successfully persisted on the non-volatile storagemedia 1310. The secondary power supply 1324 may be configured to providesufficient power for each of a plurality of such page program operationsto complete. Accordingly, the secondary power supply 1324 may beconfigured to provide sufficient power to complete double (or more) pageprogram write operations as required to store the data of the ACM 1011and/or write data pipeline 1306.

FIG. 6 is a block diagram 1500 depicting a host computing device 1014accessing an ACM using memory access semantics. The host computingdevice 1014 may comprise a processor complex/CPU 1012, which mayinclude, but is not limited to, one or more of a general purposeprocessor, an application-specific processor, a reconfigurable processor(FPGA), a processor core, a combination of processors, a processorcache, a processor cache hierarchy, or the like. In one embodiment, theprocessor complex 1012 comprises a processor cache, and the processorcache may include one or more of a write combine buffer, an L1 processorcache, an L2 processor cache, an L3 processor cache, a processor cachehierarchy, and other types of processor cache. One or more ACM users1016 (e.g., operating systems, applications, and so on) operate on thehost 1014.

The host 1014 may be communicatively coupled to the ACM 1011 via a bus1040, which may comprise a PCI-e bus, or the like. Portions of the ACM1011 are made accessible to the host 1014 may mapping in auto-commitbuffers 1013 into the host 1014. In some embodiments, mapping comprisesassociating an address range within the host memory system 1018 with anauto-commit buffer 1013 of the ACM 1011. These associations may beenabled using the SML API 1019 and/or SML 1050 available on the host1014.

The SML 1050 may comprise libraries and/or provide interfaces (e.g., SMLAPI 1019) to implement the memory access semantics described above. TheAPI 1019 may be used to access the ACM 1011 using memory accesssemantics via a memory semantic access module 1522. Other types ofaccess, such as access to the non-volatile storage 1502, may be providedvia a block device interface 1520.

The SML 1050 may be configured to memory map auto-commit buffers 1013 ofthe ACM 1011 into the memory system 1018 (via the SML API 1019). Thememory map may use a virtual memory abstraction of the memory system1018. For example, a memory map may be implemented using a memory mappedfile abstraction. In this example, the operating system (or application)1016 designates a file to be mapped into the memory system 1018. Thefile is associated with a logical identifier (LID) 1025 (e.g., logicalblock address), which may be maintained by a file system, an operatingsystem 1016, or the like.

The memory mapped file may be associated with an auto-commit buffer 1013of the ACM 1013. The association may be implemented by the SML 1050using the bus 1040. The SML 1050 associates the address range of thememory mapped file (in the memory system 1018) with a device address ofan auto-commit buffer 1013 on the ACM 1011. The association may comprisemapping a PCI-e BAR into the memory system 1018. In the FIG. 6 example,the ACM address range 1021 in the memory system 1018 is associated withthe auto-commit buffer 1013.

As discussed above, providing memory access semantics to the ACM 1011may comprise “arming” the ACM 1011 to commit data stored thereon in theevent of failure or other restart. The pre-configured arming ensuresthat, in the event of a restart, data stored on the ACM 1011 will becommitted to the proper logical identifier. The pre-configuration of thetrigger condition enables applications 1016 to access the auto-commitbuffer 1013 using “instant-commit” memory access semantics. The logicalidentifier used to arm the auto-commit buffer may be obtained from anoperating system, the memory system 1018 (e.g., virtual memory system),or the like.

The SML 1050 may be configured to arm the auto-commit buffers 1013 witha logical identifier (e.g., automatically, by callback, and/or via theSML API 1019). Each auto-commit buffer 1013 may be armed to commit datato a different logical identifier (different LBA, persistent identifier,or the like), which may allow the ACM 1011 to provide memory semanticaccess to a number of different, concurrent ACM users 1016. In someembodiments, arming an auto-commit buffer 1013 comprises setting the ACMmetadata 1015 with a logical identifier. In the FIG. 6 example, the ACMaddress range 1021 is associated with the logical identifier 1025, andthe ACM metadata 1015 of the associated auto-commit buffer is armed withthe corresponding logical identifier 1025.

The SML 1050 may arm an auto-commit buffer using an I/O control (IOCTL)command comprising the ACM address range 1021, the logical identifier1025, and/or an indicator of which auto-commit buffer 1013 is to bearmed. The SML 1050 (through the SML API 1019) may provide an interfaceto disarm or “detach” the auto-commit buffer 1013. The disarm commandmay cause the contents of the auto-commit buffer 1013 to be committed asdescribed above (e.g., committed to the non-volatile storage device1502). The detach may further comprise “disarming” the auto-commitbuffer 1013 (e.g., clearing the ACM metadata 1015). The SML 1050 may beconfigured to track mappings between address ranges in the memory system1018 and auto-commit buffers 1013 so that a detach command is performedautomatically.

Alternatively, or in addition, the SML 1050 may be integrated into theoperating system (or virtual operating system, e.g., hypervisor) of thehost 1014. This may allow the auto-commit buffers 1013 to be used by avirtual memory demand paging system. The operating system may (throughthe SML API 1019 or other integration technique) map/arm auto-commitbuffers for use by ACM users 1016. The operating system may issue commitcommands when requested by an ACM user 1016 and/or its internal demandpaging system. Accordingly, the operating system may use the ACM 1011 asanother, generally available virtual memory resource.

Once an ACM user 1016 has mapped the ACM address range 1021 to anauto-commit buffer 1013 and has armed the buffer 1013, the ACM user 1016may access the resource using memory access semantics, and may considerthe memory accesses to be “logically” committed as soon as the memoryaccess has completed. The ACM user 1016 may view the memory semanticaccesses to the ACM address range 1021 to be “instantly committed”because the ACM 1011 is configured to commit the contents of theauto-commit buffer (to the logical identifier 1025) regardless ofexperiencing restart conditions. Accordingly, the ACM user 1016 may notbe required to perform separate write and commit commands (e.g., asingle memory semantic write is sufficient to implement a write-commit).Moreover, the mapping between the auto-commit buffer 1013 and the ACM1011 disclosed herein removes overhead due to function calls, systemcalls, and even a hypervisor (if the ACM user 1016 is running in avirtual machine) that typically introduce latency into the write-commitpath. The write-commit latency time of the ACM user 1016 may thereforebe reduced to the time required to access the ACM 1011 itself.

As described above, in certain embodiments, the host 1014 may map one ormore ACM buffers 1013 into an address range of a physical memory addressspace addressable by a CPU, a kernel, or the like of the host device1014, such as the memory system 1018, as directly attached physicalmemory, as MMIO addressable physical memory over a PCI-e bus, orotherwise mapped as one or more pages of physical memory. The host 1014may further map at least a portion of the physically mapped ACM buffers1013 into a virtual memory address space, accessible to user-spaceprocesses or the like as virtual memory. The host 1014 may map theentire capacity of the physically mapped ACM buffers 1013 into a virtualmemory address space, a portion of the physically mapped ACM buffers1013 into a virtual memory address space, or the like.

In a similar manner, the host 1014 may include a virtual machinehypervisor, host operating system, or the like that maps the physicallymapped ACM buffers 1013 into an address space for a virtual machine orguest operating system. The physically mapped ACM buffers 1013 mayappear to the virtual machine or guest operating system as physicallymapped memory pages, with the virtual machine hypervisor or hostoperating system spoofing physical memory using the ACM buffers 1013. Aresource management agent, as described above, may allocate/arbitratestorage capacity of the ACM buffers 1013 among multiple virtualmachines, guest operating systems, or the like.

Because, in certain embodiments, virtual machines, guest operatingsystems, or the like detect the physically mapped ACM buffers 1013 as ifthey were simply physically mapped memory, the virtual machines cansub-allocate/arbitrate the ACM buffers 1013 into one or more virtualaddress spaces for guest processes, or the like. This allows processeswithin guest operating systems, in one embodiment, to change ACM dataand/or ACM metadata 1015 directly, without making guest operating systemcalls, without making requests to the hypervisor or host operatingsystem, or the like.

In another embodiment, instead of spoofing physical memory for a virtualmachine and/or guest operating system, a virtual machine hypervisor, ahost operating system, or the like of the host device 1014 may usepara-virtualization techniques. For example, a virtual machine and/orguest operating system may be aware of the virtual machine hypervisor orhost operating system and may work directly with it toallocate/arbitrate the ACM buffers 1013, or the like. When the ACM 1011is used in a virtual machine environment, in which one or more ACM users1016 operate within a virtual machine maintained by a hypervisor, thehypervisor may be configured to provide ACM users 1016 operating withinthe virtual machine with access to the SML API 1019 and/or SML 1050.

The hypervisor may access the SML API 1019 to associate logicalidentifiers with auto-commit buffers 1013 of the ACM 1011, as describedabove. The hypervisor may then provide one or more armed auto-commitbuffers 1013 to the ACM users 1016 (e.g., by mapping an ACM addressrange 1021 within the virtual machine memory system to the one or moreauto-commit buffers 1013). The ACM user 1016 may then access the ACM1011 using memory access semantics (e.g., efficient write-commitoperations), without incurring overheads due to, inter alia, hypervisorand other system calls. The hypervisor may be further configured tomaintain the ACM address range 1021 in association with the auto-commitbuffers 1013 until explicitly released by the ACM user 1016 (e.g., thekeep the mapping from changing during use). Para-virtualization andcooperation, in certain embodiments, may increase the efficiency of theACM 1011 in a virtual machine environment.

In some embodiments, the ACM user 1016 may be adapted to operate withthe “instant commit” memory access semantics provided by the ACM 1013.For example, since the armed auto-commit buffers 1013 are triggered tocommit in the event of a restart (without an explicit commit command),the order in which the ACM user 1016 performs memory access to the ACM1011 may become a consideration. The ACM user 1016 may employ memorybarriers, complier flags, and the like to ensure the proper ordering ofmemory access operations.

For example, read before write hazards may occur where an ACM user 1016attempts to read data through the block device interface 1520 that isstored on the ACM 1011 (via the memory semantic interface 1522). In someembodiments, the SML 1050 may maintain metadata tracking theassociations between logical identifiers and/or address ranges in thememory system 1018 and auto-commit buffers 1013. When an ACM user 1016(or other entity) attempts to access a logical identifier that is mappedto an auto-commit buffer 1013 (e.g., through the block device interface1520), the SML 1050 directs the request to the ACM 1011 (via the memorysemantic interface 1522), preventing a read before write hazard.

The SML 1050 may be configured to provide a “consistency” mechanism forobtaining a consistent state of the ACM 1011 (e.g., a barrier, snapshot,or logical copy). The consistency mechanism may be implemented usingmetadata maintained by the SML 1050, which, as described above, maytrack the triggered auto-commit buffers 1013 in the ACM 1011. Aconsistency mechanism may comprise the SML 1050 committing the contentsof all triggered auto-commit buffers 1013, such that the state of thepersistent storage is maintained (e.g., store the contents of theauto-commit buffers 1013 on the non-volatile storage 1502, or otherpersistent storage).

As described above, ACM users 1016 may access the ACM 1011 using memoryaccess semantics, at RAM granularity, with the assurance that theoperations will be committed if necessary (in the event of restart,failure, power loss, or the like). This is enabled by, inter alia, amapping between the memory system 1018 of the host 1014 andcorresponding auto-commit buffers 1013; memory semantic operationsimplemented within an ACM memory range 1021 mapped to an auto-commitbuffer 1013 are implemented directly on the buffer 1013. As discussedabove, data transfer between the host 1041 and the ACM 1011 may beimplemented using any suitable data transfer mechanism including, butnot limited to: the host 1014 performing processor IO operations (PIO)with the ACM 1011 via the bus 1040 (e.g., MMIO, PMIO, and the like); theACM 1011 (or other device) providing one or more DMA engines or agents(data movers) to transfer data between the host 1014 and the ACM 1011;the host 1014 performing processor cache write/flush operations; or thelike. Transferring data on the bus 1040 may comprise issuing a bus“write” operation followed by a “read.” The subsequent “read” may berequired where the bus 1040 (e.g., PCI bus) does not provide an explicitwrite acknowledgement.

In some embodiments, an ACM user may wish to transfer data to the ACM1011 in bulk as opposed to a plurality of small transactions. Bulktransfers may be implemented using any suitable bulk transfer mechanism.The bulk transfer mechanism may be predicated on the features of the bus1040. For example, in embodiments comprising a PCI-e bus 1040, bulktransfer operations may be implemented using bulk register store CPUinstructions.

Similarly, certain data intended for the ACM 1011 may be cached inprocessor cache of the processor complex 1012. Data that is cached in aprocessor cache may be explicitly flushed to the ACM 1011 (to particularauto-commit buffers 1013) using a CPU cache flush instruction, or thelike, such as the serializing instruction described below.

The DMA engines described above may also be used to perform bulk datatransfers between an ACM user 1016 and the ACM 1011. In someembodiments, the ACM 1011 may implement one or more of the DMA engines,which may be allocated and/or accessed by ACM users 1016 using the SML1050 (through the SML API 1019). The DMA engines may comprise local DMAtransfer engines for transferring data on a local, system bus as well asRDMA transfer engines for transferring data using a network bus, networkinterface, or the like.

In some embodiments, the ACM 1011 may be used in caching applications.For example, the non-volatile storage device 1502 may be used as cachefor other backing store, such as a hard disk, network-attached storage,or the like (not shown). One or more of the ACM 1011 auto-commit buffers1013 may be used as a front-end to the non-volatile storage 1502 cache(a write-back cache) by configuring one or more of the auto-commitbuffers 1013 of the ACM 1011 to commit data to the appropriate logicalidentifiers in the non-volatile storage 1502. The triggered buffers 1013are accessible to ACM users 1016 as described above (e.g., by mappingthe buffers 1013 into the memory system 1018 of the host 1014). Arestart condition causes the contents of the buffers 1013 to becommitted to the non-volatile storage 1502 cache. When the restartcondition is cleared, the cached data in the non-volatile storage 1502(committed by the auto-commit buffers 1013 on the restart condition)will be viewed as “dirty” in the write cache and available for useand/or migration to the backing store. The use of the ACM 1011 as acache front-end may increase performance and/or reduce wear on the cachedevice.

In some embodiments, auto-commit buffers 1013 of the ACM 1011 may beleveraged as a memory write-back cache by an operating system, virtualmemory system, and/or one or more CPUs of the host 1014. Data cached inthe auto-commit buffers 1013 as part of a CPU write-back cache may bearmed to commit as a group. When committed, the auto-commit buffers 1013may commit both data and the associated cache tags. In some embodiments,the write-back cache auto-commit buffers 1013 may be armed with an ACMaddress (or armed with a predetermined write-back cache address). Whenthe data is restored, logical identifier information, such as LBA andthe like, may be determined from a log or other data.

In some embodiments, the SML 1050 may comprise libraries and/or publishAPIs adapted to a particular set of ACM users 1016. For example, the SML1050 may provide an Instant Committed Log Library (ICL) 1552 adapted forapplications whose performance is tied to write-commit latency, such astransaction logs (database, file system, and other transaction logs),store and forward messaging systems, persistent object caching, storagedevice metadata, and the like.

The ICL 1552 provides mechanisms for mapping auto-commit buffers 1013 ofthe ACM 1011 into the memory system 1018 of an ACM user 1016 asdescribed above. ACM users 1016 (or the ICL 1552 itself) may implementan efficient “supplier/consumer” paradigm for auto-commit buffer 1013allocation, arming, and access. For example, a “supplier” thread orprocess (in the application space of the ACM users 1016) may be used toallocate and/or arm auto-commit buffers 1013 for the ACM user 1016(e.g., map auto-commit buffers 1013 to address ranges within the memorysystem 1018 of the host 1014, arm the auto-commit buffers 1013 with alogical identifier, and so on). A “consumer” thread or process of theACM user 1016 may then accesses the pre-allocated auto-commit buffers1013. In this approach, allocation and/or arming steps are taken out ofthe write-commit latency path of the consumer thread. The consumerthread of the ACM user 1016 may consider memory semantic accesses to thememory range mapped to the triggered auto-commit buffers (the ACM memoryrange 1021) as being “instantly committed” as described above.

Performance of the consumer thread(s) of the ACM user 1016 may beenhanced by configuring the supplier threads of an Instant Committed LogLibrary (ICL) 1552 (or ACM user 1016) to allocate and/or arm auto-commitbuffers 1013 in advance. When a next auto-commit buffer 1013 is needed,the ACM user 1016 have access a pre-allocated/armed buffer from a poolmaintained by the supplier. The supplier may also perform cleanup and/orcommit operations when needed. For example, if data written to anauto-commit buffer is to be committed to persistent storage, a supplierthread (or another thread outside of the write-commit path) may causethe data to be committed (using the SML API 1019). Committing the datamay comprise re-allocating and/or re-arming the auto-commit buffer 1013for a consumer thread of the ACM user 1016 as described above.

The “supplier/consumer” approach described above may be used toimplement a “rolling buffer.” An ACM user 1016 may implement anapplication that uses a pre-determined amount of “rolling” data. Forexample, an ACM user 1016 may implement a message queue that stores the“last 20 inbound messages” and/or the ACM user 1016 may managedirectives for a non-volatile storage device (e.g., persistent trimdirectives or the like). A supplier thread may allocate auto-commitbuffers 1013 having at least enough capacity to hold the “rolling data”needed by the ACM user 1016 (e.g., enough capacity to hold the last 20inbound messages). A consumer thread may access the buffers using memoryaccess semantics (load and store calls) as described above. The SML API1019 (or supplier thread of the ACM user 1016) may monitor the use ofthe auto-commit buffers 1013. When the consumer thread nears the end ofits auto-commit buffers 1013, the supplier thread may re-initialize the“head” of the buffers 1013, by causing the data to be committed (ifnecessary), mapping the data to another range within the memory system1018, and arming the auto-commit buffer 1013 with a correspondinglogical identifier. As the consumer continues to access the buffers1013, the consumer stores new data at a new location that “rolls over”to the auto-commit buffer 1013 that was re-initialized by the supplierthread, and continues to operate. In some cases, data written to therolling buffers described above may never be committed to persistentstorage (unless a restart condition or other triggering conditionoccurs). Moreover, if the capacity of the auto-commit buffers 1013 issufficient to hold the rolling data of the ACM user, the supplierthreads may not have to perform re-initialize/re-arming described above.Instead, the supplier threads may simply re-map auto-commit buffers 1013that comprise data that has “rolled over” (and/or discard the “rolledover” data therein).

In its simplest form, a rolling buffer may comprise two ACM buffers1013, and the SML 1050 may write to one ACM buffer 1013 for an ACM user1016 while destaging previously written data from the other ACM buffer1013 to a storage location, such as the non-volatile memory 1110 or thelike. In response to filling one ACM buffer 1013 and completing adestaging process of the other ACM buffer 1013, the SML 1050 maytransparently switch the two ACM buffers such that the ACM user 1016writes to the other ACM buffer 1013 during destaging of the one ACMbuffer 1013, in a ping-pong fashion. The SML 1050 may implement asimilar rolling process with more than two ACM buffers 1013. The ICL1552, in certain embodiments, includes and/or supports one or moretransactional log API functions. An ACM user 1016 may use the ICL 1552,in these embodiments, to declare or initialize a transactional log datastructure.

As a parameter to a transactional log API command to create atransactional log data structure, in one embodiment, the ICL 1552receives a storage location, such as a location in a namespace and/oraddress space of the non-volatile storage 1502 or the like, to which theSML 1050 may commit, empty, and/or destage data of the transactional logfrom two or more ACM buffers 1013 in a rolling or circular manner asdescribed above. Once an ACM user 1016 has initialized or declared atransactional log data structure, in one embodiment, the use of two ormore ACM buffers 1013 to implement the transactional log data structureis substantially transparent to the ACM user 1016, with the performanceand benefits of the ACM 1011. The use of two or more ACM buffers 1013,in certain embodiments, is transparent when the destage rate for the twoor more ACM buffers 1013 is greater than or equal to the rate at whichthe ACM user 1016 writes to the two or more ACM buffers 1013. The ICL1552, in one embodiment, provides byte-level writes to a transactionallog data structure using two or more ACM buffers 1013.

In another example, a supplier thread may maintain four (4) or more ACMbuffers 1013. A first ACM buffer 1013 may be armed and ready to acceptdata from the consumer, as described above. A second ACM buffer 1013 maybe actively accessed (e.g., filled) by a consumer thread, as describedabove. A third ACM buffer 1013 may be in a pre-arming process (e.g.,re-initializing, as described above), and a fourth ACM buffer 1013 maybe “emptying” or “destaging” (e.g., committing to persistent storage, asdescribed above).

In some embodiments, the ICL 1552 and/or rolling log mechanismsdescribed above may be used to implement an Intent Log for SynchronousWrites for a filesystem (e.g., the ZFS file system). The log data (ZIL)may be fairly small (1 to 4 gigabytes) and is typically “write only.”Reads may only be performed for file system recovery. One or moreauto-commit buffers 1013 may be used to store filesystem data using arolling log and/or demand paging mechanism as described above.

The ICL library 1552 may be configured to operate in a high-availabilitymode as described above in conjunction with FIG. 4. In ahigh-availability mode, the SML 1050 and/or bus 1040 sends commandspertaining to memory semantic accesses to two or more ACM 1011, each ofwhich may implement the requested operations and/or be triggered tocommit data in the event of a restart condition.

The ACM 1011 disclosed herein may be used to enable other types ofapplications, such as durable synchronization primitives. Asynchronization primitive may include, but is not limited to: asemaphore, mutex, atomic counter, test and set, or the like.

A synchronization primitive may be implemented on an auto-commit buffer1013. ACM users 1016 (or other entities) that wish to access thesynchronization primitive may map the auto-commit buffer 1013 into thememory system 1018. In some embodiments, each ACM user 1016 may map thesynchronization primitive auto-commit buffer 1013 into its own,respective address range in the memory system 1018. Since the differentaddress ranges are all mapped to the same auto-commit buffer 1013, allwill show the same state of the synchronization primitive. ACM users1016 on remote computing devices may map the synchronization primitiveauto-commit buffer 1013 into their memory system using an RDMA networkor other remote access mechanism (e.g., Infiniband, remote PCI, etc.).

In some embodiments, the SML 1050 may comprise a Durable SynchronizationPrimitive Library (DSL) 1554 to facilitate the creation of and/or accessto synchronization primitives on the ACM 1011. The DSL 1554 may beconfigured to facilitate one-to-many mappings as described above (oneauto-commit buffer 1030-to-many address ranges in the memory system1018).

The ACM users 1016 accessing the semaphore primitive may consider theiraccesses to be “durable,” since if a restart condition occurs while thesynchronization primitive is in use, the state of the synchronizationprimitive will be persisted as described above (the auto-commit buffer1013 of the synchronization primitive will be committed to thenon-volatile storage 1502, or other persistent storage).

As described above, the SML 1050 may be used to map a file into thememory system 1018 (virtual address space) of the host 1014. The filemay be mapped in an “Instant Committed Memory” (ICM) mode. In this mode,all changes made to the memory mapped file are guaranteed to bereflected in the file, even if a restart condition occurs. Thisguarantee may be made by configuring the demand paging system to use anauto-commit buffer 1013 of the ACM 1011 for all “dirty” pages of the ICMfile. Accordingly, when a restart condition occurs, the dirty page willbe committed to the file, and no data will be lost.

In some embodiments, the SML 1050 may comprise an ICM Library (ICML)1556 to implement these features. The ICML 1556 may be integrated withan operating system and/or virtual memory system of the host 1014. Whena page of an ICM memory mapped file is to become dirty, the ICML 1556prepares an auto-commit buffer 1013 to hold the dirty page. Theauto-commit buffer 1013 is mapped into the memory system 1018 of thehost 1014, and is triggered to commit to a logical identifier associatedwith the memory mapped file. As described above, changes to the pages inthe memory system 1018 are implemented on the auto-commit buffer 1013(via the memory semantic access module 1522).

The ICML 1556 may be configured to commit the auto-commit buffers 1013of the memory mapped file when restart conditions occur and/or when thedemand paging system of the host 1014 needs to use the auto-commitbuffer 1013 for another purpose. The determination of whether to“detach” the auto-commit buffer 1013 from a dirty page may be made bythe demand paging system, by the SML 1050 (e.g., using a least recentlyused (LRU) metric, or the like), or by some other entity (e.g., an ACMuser 1016). When the auto-commit buffer is detached, the SML 1050 maycause its contents to be committed. Alternatively, the contents of theauto-commit buffer 1013 may be transferred to system RAM at which pointthe virtual memory mapping of the file may transition to use a RAMmapping mechanisms.

In some embodiments, the SML 1050 (or ICML 1556) may be configured toprovide a mechanism to notify the operating system (virtual memorysystem or the like) that a page of a memory mapped file is about tobecome dirty in advance of an ACM user 1016 writing the data. Thisnotification may allow the operating system to prepare an auto-commitbuffer 1013 for the dirty page in advance, and prevent stalling when thewrite actually occurs (while the auto-commit buffer is mapped andarmed). The notification and preparation of the auto-commit buffer 1013may implemented in a separate thread (e.g., a supplier thread asdescribed above).

The SML 1050 and/or ICML 1556 may provide an API to notify the operatingsystem that a particular page that is about to be written has no usefulcontents and should be zero filled. This notification may help theoperating system to avoid unnecessary read operations.

The mechanisms for memory mapping a file to the ACM 1011 may be used inlog-type applications. For example, the ICL library 1552 may beimplemented to memory map a log file to one or more auto-commit buffers1013 as described above. A supplier thread may provide notifications tothe operating system regarding which pages are about to become dirtyand/or to identify pages that do not comprise valid data.

Alternatively, or in addition, the ICML 1556 may be implemented withoutintegration into an operating system of the host 1014. In theseembodiments, the ICML 1556 may be configured to monitor and/or trapsystem signals, such as mprotect, mmap, and manual segmentation faultsignals to emulate the demand paging operations typically performed byan operating system.

FIG. 7 is a flow diagram of one embodiment of a method 1600 forproviding an auto-commit memory. At step 1610 the method 1600 may startand be initialized. Step 1610 may comprise the method 1600 initiatingcommunication with an ACM over a bus (e.g., initiating communicationwith ACM 1011 via bus 1040).

At step 1620, an auto-commit buffer of the ACM may be mapped into thememory system of a computing device (e.g., the host 1014). The mappingmay comprise associating a BAR address of the auto-commit buffer with anaddress range in the memory system.

At step 1630, the auto-commit buffer may be armed with ACM metadataconfigured to cause the auto-commit buffer to be committed to aparticular persistent storage and/or at a particular location in thepersistent storage in the event of a restart condition. In someembodiments, the ACM metadata may comprise a logical identifier such asa LBA, object identifier, or the like. Step 1630 may comprise verifyingthat the ACM metadata is valid and/or can be used to commit the contentsof the auto-commit buffer.

At step 1640, an ACM user, such as an operating system, application, orthe like, may access the armed auto-commit buffer using memory accesssemantics. The ACM user may consider the accesses to be “instantlycommitted” due to the arming of step 1630. Accordingly, the ACM user mayimplement “instant committed” writes that omit a separate and/orexplicit commit command. Moreover, since the memory semantic accessesare directly mapped to the auto-commit buffer (via the mapping of step1620), the memory semantic accesses may bypass systems calls typicallyrequired in virtual memory systems.

At step 1650 the method 1600 ends until a next auto-commit buffer ismapped and/or armed.

FIG. 8 is a flow diagram of another embodiment of a method 1700 forproviding an auto-commit memory. At step 1710 the method 1700 starts andis initialized as described above.

At step 1720, an auto-commit buffer of an ACM is mapped into the memorysystem of a computing device (e.g., the host 1014), and is armed asdescribed above.

At step 1730, an ACM user accesses the auto-commit buffer using memoryaccess semantics (e.g., by implementing memory semantic operationswithin the memory range mapped to the auto-commit buffer at step 1720).

At step 1740, a restart condition is detected. As described above, therestart condition may be a system shutdown, a system restart, a loss ofpower, a loss of communication between the ACM and the host computingdevice, a software fault, or any other restart condition that precludescontinued operation of the ACM and/or the host computing device.

At step 1750, the ACM implements the armed triggered commit actions onthe auto-commit buffer. The triggered commit action may comprisecommitting the contents of the auto-commit buffer to persistent storage,such as a solid-state or other non-volatile storage or the like.

At step 1760, the method 1700 ends until a next auto-commit buffer ismapped and/or armed or a restart condition is detected.

FIG. 9 is a flow diagram of another embodiment for providing anauto-commit memory. At step 1810, the method 1800 starts and isinitialized as described above. At step 1820, a restart condition isdetected.

At step 1830, the method 1800 accesses armed auto-commit buffers on theACM (if any). Accessing the armed auto-commit buffer may comprise themethod 1800 determining whether an auto-commit buffer has been armed byinspecting the triggered ACM metadata thereof. If no triggered ACMmetadata exists, or the ACM metadata is invalid, the method 1800 maydetermine that the auto-commit buffer is not armed. If valid triggeredACM metadata does exist for a particular auto-commit buffer, the method1800 identifies the auto-commit buffer as an armed buffer and continuesto step 1840.

At step 1840, the triggered commit action for the armed auto-commitbuffers is performed. Performing the triggered commit action maycomprise persisting the contents of the auto-commit buffer to asequential and/or log-based storage media, such as a solid-state orother non-volatile storage media. Accordingly, the triggered commitaction may comprise accessing a logical identifier of the auto-commitbuffer, labeling the data with the logical identifier, and injecting thelabeled data into a write data pipeline. Alternatively, the triggeredcommit action may comprise storing the data on a persistent storagehaving a one-to-one mapping between logical identifier and physicalstorage address (e.g., a hard disk). The triggered commit action maycomprise storing the contents of the armed auto-commit buffer to thespecified physical address.

Performing the triggered commit action at step 1840 may comprise using asecondary power supply to power the ACM, solid-state storage medium,and/or other persistent, non-volatile storage medium, until thetriggered commit actions are completed.

In certain embodiments, instead of or in addition to using a volatilememory namespace, such as a physical memory namespace, a virtual memorynamespace, or the like and/or instead of or in addition to using astorage namespace, such as a file system namespace, a logical unitnumber (LUN) namespace, or the like, one or more commit agents 1020, asdescribed above, may implement an independent persistent memorynamespace for the ACM 1011. For example, a volatile memory namespace,which is typically accessed using an offset in physical and/or virtualmemory, is not persistent or available after a restart event such as areboot, failure event, or the like and a process that owned the data inphysical and/or virtual memory prior to the restart event typically nolonger exists after the restart event. Alternatively, a storagenamespace is typically accessed using a file name and an offset, a LUNID and an offset, or the like. While a storage namespace may beavailable after a restart event, a storage namespace may have too muchoverhead for use with the ACM 1011. For example, saving a state for eachexecuting process using a file system storage namespace may result in aseparate file for each executing process, which may not be an efficientuse of the ACM 1011.

The one or more commit agents 1020 and/or the controller 1004, incertain embodiments, provide ACM users 1016 with a new type ofpersistent memory namespace for the ACM 1011 that is persistent throughrestart events without the overhead of a storage namespace. One or moreprocesses, such as the ACM user 1016, in one embodiment, may access thepersistent memory namespace using a unique identifier, such as aglobally unique identifier (GUID), universal unique identifier (UUID),or the like so that data stored by a first process for an ACM user 1016prior to a restart event is accessible to a second process for the ACMuser 1016 after the restart event using a unique identifier, without theoverhead of a storage namespace, a file system, or the like.

The unique identifier, in one embodiment, may be assigned to an ACM user1016 by a commit agent 1020, the controller 1004, or the like. Inanother embodiment, an ACM user 1016 may determine its own uniqueidentifier. In certain embodiments, the persistent memory namespace issufficiently large and/or ACM users 1016 determine a unique identifierin a predefined, known manner (e.g., based on a sufficiently unique seedvalue, nonce, or the like) to reduce, limit, and/or eliminate collisionsbetween unique identifiers. In one embodiment, the ACM metadata 1015includes a persistent memory namespace unique identifier associated withan owner of an ACM buffer 1013, an owner of one or more pages of an ACMbuffer 1013, or the like.

In one embodiment, the one or more commit agents 1020 and/or thecontroller 1004 provide a persistent memory namespace API to ACM users1016, over which the ACM users 1016 may access the ACM 1011 using thepersistent memory namespace. In various embodiments, the one or morecommit agents 1020 and/or the controller 1004 may provide a persistentmemory namespace API function to transition, convert, map, and/or copydata from an existing namespace, such as a volatile memory namespace ora storage namespace, to a persistent memory namespace; a persistentmemory namespace API function to transition, convert, map, and/or copydata from a persistent memory namespace to an existing namespace, suchas a volatile memory namespace or a storage namespace; a persistentmemory namespace API function to assign a unique identifier such as aGUID, a UUID, or the like; a persistent memory namespace API function tolist or enumerate ACM buffers 1013 associated with a unique identifier;a persistent memory namespace API function to export or migrate dataassociated with a unique identifier so that an ACM user 1016 such as anapplication and/or process may take its ACM data to a different host1014, to a different ACM 1011, or the like; and/or other persistentmemory namespace API functions for the ACM 1011.

For example, an ACM user 1016, in one embodiment, may use a persistentmemory namespace API function to map one or more ACM buffers 1013 of apersistent memory namespace into virtual memory of an operating systemof the host 1014, or the like, and the mapping into the virtual memorymay end in response to a restart event while the ACM user 1016 maycontinue to access the one or more ACM buffers 1013 after the restartevent using the persistent memory namespace. In certain embodiments, theSML 1050 may provide the persistent memory namespace API in cooperationwith the one or more commit agents 1020 and/or the controller 1004.

The persistent memory namespace, in certain embodiments, is a flatnon-hierarchical namespace of ACM buffers 1013 (and/or associated ACMpages), indexed by the ACM metadata 1015. The one or more commit agents1020 and/or the controller 1004, in one embodiment, allow the ACMbuffers 1013 to be queried by ACM metadata 1015. In embodiments wherethe ACM metadata 1015 includes a unique identifier, in certainembodiments, an ACM user 1016 may query or search the ACM buffers 1013by unique identifier to locate ACM buffers 1013 (and/or stored data)associated with a unique identifier. In a further embodiment, the one ormore commit agents 1020 and/or the controller 1004 may provide one ormore generic metadata fields in the ACM metadata 1015 such that an ACMuser 1016 may define its own ACM metadata 1015 in the generic metadatafield, or the like. The one or more commit agents 1020 and/or thecontroller 1004, in one embodiment, may provide access control for theACM 1011, based on unique identifier, or the like.

In one embodiment, an ACM buffer 1013 may be a member of a persistentmemory namespace and one or more additional namespaces, such as avolatile namespace, a storage namespace or the like. In a furtherembodiment, the one or more commit agents 1020 and/or the controller1004 may provide multiple ACM users 1016 with simultaneous access to thesame ACM buffers 103. For example, multiple ACM users 1016 of the sametype and/or with the same unique identifier, multiple instances of asingle type of ACM user 1016, multiple processes of a single ACM user1016, or the like may share one or more ACM buffers 1013. Multiple ACMusers 1016 accessing the same ACM buffers 1013, in one embodiment, mayprovide their own access control for the shared ACM buffers 1013, suchas a locking control, turn-based control, moderator-based control, orthe like. In a further embodiment, using a unique identifier, a new ACMuser 1016, an updated ACM user 1016, or the like on the host 1014 mayaccess

In certain embodiments, the ACM 1011 may comprise a plurality ofindependent access channels, buses, and/or ports, and may be at leastdual ported (e.g., dual ported, triple ported, quadruple ported). Inembodiments where the ACM 1011 is at least dual ported, the ACM 1011 isaccessible over a plurality of independent buses 1040. For example, theACM 1011 may be accessible over redundant bus 1040 connections with asingle host 1014, may be accessible to a plurality of hosts 1014 overseparate buses 104 with the different hosts 1014, or the like. Inembodiments where the ACM 1011 is at least dual ported, if one nodeand/or access channel fails (e.g., a host 1014, a bus 1040), one or moreadditional nodes and/or access channels to the ACM 1011 remainfunctional, obviating the need for redundancy, replication, or the likebetween multiple hosts 1014.

In one embodiment, the ACM 1011 comprises a PCI-e attached dual portdevice, and the ACM 1011 may be connected to and in communication withtwo hosts 1014 over independent PCI-e buses 1040. For example, the ACM1011 may comprise a plurality of PCI-e edge connectors for connecting toa plurality of PCI-e slot connectors, or the like. In a furtherembodiment, the power connection 1030 may also be redundant, with onepower connection 1030 per bus 1040 or the like. At least one of theplurality of connections, in certain embodiments, may comprise a datanetwork connection such as a NIC or the like. For example, the ACM 1011may comprise one or more PCI-e connections and one or more data networkconnections.

In one embodiment, the controller 1004 may arbitrate between a pluralityof hosts 1014 to which the ACM 1011 is coupled, such that one host 1014may access the ACM buffers 1013 at a time. The controller 1004, inanother embodiment, may accept a reservation request from a host 1014and may provide the requesting host 1014 with access to the ACM buffers1013 in response to receiving the reservation request. The ACM 1011 maynatively support a reservation request as an atomic operation of the ACM1011. In other embodiments, the ACM 1011 may divide ACM buffers 1013between hosts 1014, may divide ACM buffers 1013 between hosts but sharebacking non-volatile memory 1110 between hosts, or may otherwise dividethe ACM buffers 1013, the non-volatile memory 1110, and/or associatedaddress spaces between hosts 1014.

In one embodiment, the controller 1004, the one or more commit agents1020, and/or other elements of the ACM 1011 may be dual-headed,split-brained, or the like, each head or brain being configured tocommunicate with a host 1014 and with each other to provide redundantfunctions for the ACM 1011. By being at least dual ported, in certainembodiments, the ACM 1011 may be redundantly accessible, without theoverhead of replication, duplication, or the like which would otherwisereduce I/O speeds of the ACM 1011, especially if such replication,duplication, were performed over a data network or the like.

FIG. 10A depicts one embodiment of an ACM module 1317. The ACM module1317, in certain embodiments, may be substantially similar to the ACMmodule 1317 described above with regard to FIG. 5. In other embodiments,the ACM module 1317 may include, may be integrated with, and/or may bein communication with the SML 1050, the storage controller 1004, 1104,1304, and/or the commit agent 1020.

In general, the ACM module 1317 services auto-commit requests from anACM user 1016 or other client for the ACM 1011. As described above withregard to the ACM users 1016, as used herein, a client may comprise oneor more of an operating system (OS), virtual operating platform (e.g.,an OS with a hypervisor), guest OS, application, process, thread,entity, utility, user, or the like, that is configured to access or usethe ACM 1011. In the depicted embodiment, the ACM module 1317 includes arequest module 1902, a mapping module 1904, and a bypass module 1906.The ACM module 1317, in certain embodiments, provides an interfacewhereby an ACM user 1016 or other client may access data stored in thebyte addressable ACM buffers 1013, whether the ACM buffers 1013 arenatively volatile or non-volatile, regardless of the type of media usedfor the ACM buffers 1013.

Instead of or in addition to the above methods of accessing the ACM1011, such as using a memory map (e.g., mmap) interface, in certainembodiments, the ACM module 1317 may expose the auto-commit buffers 1013directly to ACM users 1016 or other clients, bypassing one or moreoperating system and/or kernel layers, which may otherwise reduceperformance of the ACM 1011, increasing access times, introducingdelays, or the like. The ACM module 1317 may provide access to the ACM1011 using an existing I/O interface, such as a standard read/write APIor the like, so that ACM users 1016 or other clients may access the ACM1011 and receive its benefits with little or no modification orcustomization. In another embodiment, the ACM module 1317 may provide acustom or modified ACM interface, which may provide ACM users 1016 andother clients more control over operation of the ACM 1011 than may beprovided by existing interfaces.

As described above, in certain embodiments, the ACM module 1317 and/orthe ACM 1011 enable clients such as the ACM users 1016 to access fast,byte-addressable, persistent memory, combining benefits of volatilememory and non-volatile storage. Auto-commit logic inside the hardwareof the storage device 102, such as the auto-commit memory 1011 describedabove with regard to FIG. 1, in certain embodiments, provides power-cutprotection for data written to the auto-commit buffers 1013 of the ACM1011. The ACM module 1317 and/or its sub-modules, in variousembodiments, may at least partially be integrated with a device driverexecuting on the processor 1012 of the host computing device 1014 suchas the SML 1050, may at least partially be integrated with a hardwarecontroller 1004, 1104 of the ACM 1011 and/or non-volatile storage device1102, as microcode, firmware, logic circuits, or the like, or may bedivided between a device driver and a hardware controller 1004, 1104, orthe like.

In one embodiment, the request module 1902 is configured to monitor,detect, intercept, or otherwise receive requests for data of thenon-volatile memory device 1102 from clients, such as the ACM users 1016described above, another module, a host computing device 1014, or thelike. The request module 1902 may receive data requests over an API, ashared library, a communications bus, or another interface. As usedherein, a data request may comprise a storage request, a memory request,an auto-commit request, or the like to access data, such as the open,read, write, trim, load, and/or store requests described above.

The request module 1902 may receive data requests using an existing orstandard I/O interface, such as read and write requests over the blockdevice interface 1520, load and store commands over the memory semanticinterface 1522, or the like. By using the auto-commit buffers 1013 tosupport standard requests or commands, in certain embodiments, therequest module 1902 may allow the ACM users 1016 or other clients toaccess the ACM 1011 transparently, with little or no modification orcustomization using the standard requests or commands. For example, anACM user 1016 may send data requests to the request module 1902 over theblock device interface 1520, the memory semantic interface 1522, or thelike using standard requests or commands, with no knowledge of whetherthe ACM module 1317 services or satisfies the request using theauto-commit buffers 1013 or the non-volatile memory media 1110, allowingthe mapping module 1904 described below to dynamically determine how toallocate data between the non-volatile memory media 1110 and theauto-commit buffers 1013. The request module 1902 may intercept datarequests using an existing or standard interface using a filter driver,overloading an interface, using LD_PRELOAD, intercepting or trapping asegmentation fault, or the like.

In certain embodiments, the request module 1902 may receive datarequests using a custom or modified ACM interface, such as an ACM API,the SML API 1019, or the like. Data requests received over a custom ormodified interface, in certain embodiments, may indicate whether arequesting ACM user 1016 or other client intends the data request to beserviced using the auto-commit buffers 1013 or the non-volatile memorymedium 1102 (e.g., whether data of the request is to be associated withthe auto-commit buffers 1013 or the non-volatile memory medium 1102).For example, the request module 1902 may receive data requests includingan auto-commit flag indicating whether data of the request is associatedwith or is to be associated with an auto-commit buffer 1013 of the ACM1011. An auto-commit flag may comprise a bit, a field, a variable, aparameter, a namespace identifier or other logical identifier, oranother indicator.

In certain embodiments, instead of a separate auto-commit flag, a datarequest may indicate whether the data is associated with an auto-commitbuffer 1013 or with the non-volatile memory media 1110 based on anamespace identifier or other logical indicator of the data request. Asused herein, a namespace comprises a container or range of logical orphysical identifiers that index or identify data, data locations, or thelike. As described above, examples of namespaces may include a filesystem namespace, a LUN namespace, a logical address space, a storagenamespace, a virtual memory namespace, a persistent ACM namespace, avolatile memory namespace, an object namespace, a network namespace, aglobal or universal namespace, a BAR namespace, or the like.

A namespace identifier, as used herein, comprises an indication of anamespace to which data belongs. In one embodiment, a namespaceidentifier may comprise a logical identifier, as described above. Forexample, a namespace identifier may include a file identifier and/or anoffset from a file system namespace, a LUN ID and an offset from a LUNnamespace, an LBA or LBA range from a storage namespace, one or morevirtual memory addresses from a virtual memory namespace, an ACM addressfrom a persistent ACM namespace, a volatile memory address from avolatile memory namespace of the host device 1014, an object identifier,a network address, a GUID, UUID, or the like, a BAR address or addressrange from a BAR namespace, or another logical identifier. In a furtherembodiment, a namespace identifier may comprise a label or a name for anamespace, such as a directory, a file path, a device identifier, or thelike. In another embodiment, a namespace identifier may comprise aphysical address or location for data. As described above, certainnamespaces, and therefore namespace identifiers, may be temporary orvolatile, and may not be available to an ACM user 1016 after a restartevent. Other namespaces, and therefore namespace identifiers, may bepersistent, such as a file system namespace, a LUN namespace, apersistent ACM namespace, or the like, and data associated with thepersistent namespace may be accessible to an ACM user 1016 or otherclient after a restart event using the persistent namespace identifier.

An address or range of addresses may be associated with a namespace ifthe address or range of addresses comprises an identifier from thenamespace, if the address or range of addresses is mapped into thenamespace, or the like. Data or a range of data may be associated with anamespace if the data is stored in a storage medium of the namespace,such as the auto-commit buffers 1013 or the non-volatile memory media1102, if the data is mapped to the namespace in a logical-to-physicalmapping structure, if the data is associated with a namespace identifierfor the namespace, or the like.

A logical namespace may be associated with both the auto-commit buffers1013 and the non-volatile memory media 1110, with different logicalidentifiers from the logical namespace mapped to different physicalidentifiers or locations for the auto-commit buffers 1013 and/or thenon-volatile memory media 1110. For example, certain data associatedwith file identifiers of a file system may be stored in the auto-commitbuffers 1013 while other data associated with file identifiers of thefile system may be stored in the non-volatile memory media 1110, evendata at different offsets within the same file.

The request module 1902 may receive an open request to initialize anamespace identifier or other logical identifier, such as opening a fileor the like. The request module 1902 may receive a write request, astore request, or the like to store data in the auto-commit buffers 1013and/or the non-volatile memory medium 1110 of the non-volatile memorydevice 1102. The request module 1902 may receive a read request, a loadrequest, or the like to read data from the auto-commit buffers 1013and/or the non-volatile memory medium 1110 of the non-volatile memorydevice 1102. In one embodiment, a namespace identifier of a data requestidentifies both a namespace for and data of the data request, such asthe logical identifiers described above. In another embodiment, a datarequest may comprise both a namespace identifier and a separate logicalidentifier for the data.

The request module 1902, in certain embodiments, may receive datarequests in user-space. As used herein, kernel-space may comprise anarea of memory (e.g., volatile memory, virtual memory, main memory) ofthe host computing device 1014; a set of privileges, libraries, orfunctions; a level of execution; or the like reserved for a kernel,operating system, or other privileged or trusted processes orapplications. User-space, as used herein, may comprise an area of memory(e.g., volatile memory, virtual memory, main memory) of the hostcomputing device 1014; a set of privileges, libraries, or functions; alevel of execution; or the like available to untrusted, unprivilegedprocesses or applications.

Due to access control restrictions, privilege requirements, or the likefor kernel-space, providing a device driver, library, API, or the likefor the ACM 1011 in kernel-space may have greater delays than inuser-space. Further, use of a storage stack of a kernel or operatingsystem, in certain embodiments, may introduce additional delays. Anoperating system or kernel storage stack, as used herein, may compriseone or more layers of device drivers, translation layers, file systems,caches, and/or interfaces provided in kernel-space, for accessing a datastorage device. As described in greater detail below, with regard to thebypass module 1906, the ACM module 1317 may provide direct access to theACM 1011 by bypassing and/or replacing one or more layers of anoperating system or kernel storage stack, reading and writing datadirectly between the ACM buffers 1013 and user-space or the like.

In one embodiment, the mapping module 1904 is configured to map orassociate namespace identifiers, logical identifiers, or the like to theACM buffers 1013 and/or the non-volatile memory media 1110. In certainembodiments, the mapping module 1904 may maintain a logical-to-physicalmapping structure, as described below with regard to FIG. 11, mappinglogical identifiers or other namespace identifiers to physical locationsin the non-volatile memory media 1110 and/or the ACM buffers 1013. Inone embodiment, the mapping module 1904 may access and/or maintainseparate logical-to-physical mapping structures, one for thenon-volatile memory media 1110 and one for the ACM buffers 1013. Asdescribed above, in certain embodiments, the ACM buffers 1013 and thenon-volatile memory media 1110 may be accessible and/or addressable atdifferent granularities. For example, the ACM buffers 1013 may bebyte-addressable, while the non-volatile memory media 1110 may beblock-addressable (e.g., 512 byte blocks, 4 KiB blocks, or the like).

In response to the request module 1902 receiving a data request for arange of data, for a logical identifier or other namespace identifier,or the like, such as an open request, a write request, a read request, aload request, a store request, or the like, the mapping module 1904 maydetermine whether there is a relationship between the data and/ornamespace identifier and one or more auto-commit buffers 1013. Dataand/or a logical identifier or other namespace identifier for the datamay have a relationship with an auto-commit buffer 1013 if the data isstored in the auto-commit buffer 1013, if the data is targeted for orintended to be stored in the auto-commit buffer 1013, if the data isidentified in a data request for an auto-commit buffer 1013, or thelike. The mapping module 1904, in one embodiment, may determine whetheran existing association or mapping exists between requested data and/ora namespace identifier and the auto-commit buffers 1013. In a furtherembodiment, the mapping module 1904 may determine whether or not to mapor create an association between requested data and an auto-commitbuffer 1013.

In one embodiment, the mapping module 1904 maps or associates data withan auto-commit buffer 1013 in response to an auto-commit flag of a datarequest for the data, as described above. For example, as describedabove, in embodiments where the request module 1902 receives datarequests over a custom or extended interface, an ACM user 1016 or otherclient may indicate which data is to be stored in and associated withthe auto-commit buffers 1013, using auto-commit flags or otherindicators.

In a further embodiment, where the request module 1902 receives datarequests transparently, using an existing, standard interface or thelike, the mapping module 1904 may dynamically determine which data isstored in and associated with the auto-commit buffers 1013 and whichdata is stored in the non-volatile memory media 1110. The mapping module1904 may be configured to optimally distribute data between theauto-commit buffers 1013 and the non-volatile memory media 1110, basedon one or more efficiency factors for namespace identifiers, for data,or the like. An efficiency factor, as used herein, may comprise anindicator or representation of an effect or impact of storing orassociating data within the auto-commit buffers 1013.

The mapping module 1904 may monitor or track efficiency factors fordifferent data, different ACM users 1016, different namespaceidentifiers, or the like. In one embodiment, an efficiency factor mayinclude an access frequency for data. For example, the mapping module1904 may be more likely to store data in the auto-commit buffers 1013that is more frequently accessed. In various embodiments, efficiencyfactors may include a size of data, a type of data, a quality of service(QoS) for data or for an ACM user 1016, a service level agreement withan ACM user 1016, an age of data, an amount of available storagecapacity in the auto-commit buffers 1013 and/or in the non-volatilememory medium 1110, or the like. The mapping module 1904 may balance orweigh multiple efficiency factors to determine whether to associate orstore data of a certain namespace identifier or range of namespaceidentifiers with the auto-commit buffers 1013.

In one embodiment, the mapping module 1904 cooperates with the SML 1050to determine mappings for data in a logical address space or othernamespace of the non-volatile memory media 1110 and to preserve themappings as metadata 1051 or a forward index 1053, such as thelogical-to-physical mapping structure described below with regard toFIG. 11. In other embodiments, the mapping module 1904 may cooperatewith an operating system, a file manager, a storage stack, a memorysystem 1018, or the like to create mappings, to assign namespaceidentifiers, or the like.

In certain embodiments, mapping a namespace identifier, such as afilename and an offset, to an ACM buffer 1013, or otherwise initializingor creating a mapping may be a privileged operation, performed inkernel-space or the like. The mapping module 1904 may use an IOCTL call,a shared memory queue between user-space and kernel-space, or the likeso that data requests for the auto-commit buffers 1013 can be servicedor satisfied from user-space, while mappings may be performed, at leastpartially, in kernel-space. In one embodiment, the mapping module 1904,as part of or in addition to mapping namespace identifiers such asfilenames and offsets to the auto-commit buffers 1013, maps theassociated page of an ACM buffer 1013 into a virtual address space ofthe requesting ACM user 1016, as described above, so that the data isaccessible to the ACM user 1016 as virtual memory of the host computingdevice 1014.

The mapping module 1904 may map and/or store an entire data object, suchas a file or the like, to an ACM buffer 1013. In certain embodiments,the mapping module 1904 may map and/or store a portion of a data object,such as a particular offset or range of data within a file, to an ACMbuffer 1013. The mapping module 1904 may map and/or store the remainderof a file mapped partially to an ACM buffer 1013 to the non-volatilememory media 1110.

The mapping module 1904, in certain embodiments, cooperates with the ACMmodule 1317 and/or a commit agent 1020 to arm ACM buffers 1013 with ACMmetadata 1015 including mappings of namespace identifiers, or the like,so that the ACM buffers 1013 are configured to perform appropriatecommit actions for the data in the ACM buffers 1013 to remainpersistently associated with the namespace identifiers, even after arestart event. In this manner, the ACM users 1016 may continue to accessthe data using the same namespace identifiers even after the restartevent. As described above, the ACM metadata 1015 may include multiplesections, or parts. In one embodiment, the ACM metadata 1015 includes alogical identifier to which the ACM buffer 1013 is to commit the data inthe non-volatile memory media 1110 (e.g., an LBA or the like) and anamespace identifier (e.g., a filename, a filename and an offset, aninode number, a LUN address, or the like) for the data, which the commitagent 1020 may use to recover the data after a restart event, allowingthe ACM users 1016 to continue to access the data using the namespaceidentifier.

In one embodiment, the bypass module 1906 is configured to serviceand/or satisfy requests that the request module 1902 receives, using theACM buffers 1013 and/or the non-volatile memory media 1110. In responseto the mapping module 1904 determining that a namespace identifier of adata request is associated with the ACM buffers 1013, the bypass module1906 may service or satisfy the data request using the ACM buffers 1013(e.g., storing the data in the ACM buffers 1013 in response to a writeor store request, reading the data from the ACM buffers 1013 in responseto a read or load request, or the like).

In certain embodiments, the bypass module 1906 services or satisfiesdata requests directly from the ACM buffers 1013, accessing hardware ofthe ACM buffers 1013 directly from user-space without using an operatingsystem or kernel storage stack, writing data directly to the ACM buffers1013, reading data directly from the ACM buffers 1013, or the like. Thebypass module 1906, in embodiments where one or more pages of the ACMbuffers 1013 are mapped into virtual memory of an ACM user 1016 on thehost device 1014, may access the hardware of the ACM buffers 1013directly and copy data from the ACM buffers 1013 directly into or fromthe virtual memory at an offset indicated by a namespace identifier ofthe data request from user-space, without any kernel-space libraries,calls, memory accesses, or the like.

For example, the bypass module 1906 may be integrated with and/orcooperate with a user-space device driver for the non-volatile memorydevice 1102, executing on the processor 1012 of the host device 1014,and may service or satisfy data requests by mapping or copying data toand from hardware of the auto-commit buffers 1013 and a virtual memoryof a requesting client, such as a shared virtual memory for a pluralityof ACM users 1016, separate virtual memory spaces of different ACM users1016, or the like, all from user-space. By servicing data requests inuser-space, directly from an auto-commit buffer 1013 without passingthrough an operating system or kernel storage stack, in certainembodiments, the bypass module 1906 may reduce operating system orkernel overhead associated with accessing the non-volatile memory device1102, decrease access times, or the like.

For data requests that the mapping module 1904 determines are notassociated with an auto-commit buffer 1013, the bypass module 1906 mayservice or satisfy the requests using the non-volatile memory medium1110 (e.g., storing the data in the non-volatile memory medium 1110 inresponse to a write request, reading the data from the non-volatilememory medium 1110 in response to a read request, or the like). Forcertain data requests, the mapping module 1904 may determine that arange of data and/or range of namespace identifiers is partiallyassociated with the auto-commit buffers 1013 and partially associatedwith the non-volatile memory medium 1110, and the bypass module 1906 maysplit the data request, satisfying it partially from the auto-commitbuffers 1013 and partially from the non-volatile memory medium 1110, mayconsolidate the data in either the auto-commit buffers 1013 or thenon-volatile memory medium 1110, or the like.

FIG. 10B depicts another embodiment of an ACM module 1317. In oneembodiment, the ACM module 1317 may be substantially similar to one ormore of the ACM modules 1317 described above with regard to FIGS. 5 and10A. In the depicted embodiment, the ACM module 1317 of FIG. 10Bincludes a request module 1902, a mapping module 1904, and a bypassmodule 1906 and further includes a has-been-written module 1908 and asecurity module 1910. The bypass module 1906 in FIG. 10B includes a readmodule 1912 and a write module 1914. In one embodiment, the requestmodule 1902 and the mapping module 1904 are substantially similar to therequest module 1902 and the mapping module 1904 described above withregard to FIG. 10A.

In one embodiment, the bypass module 1906 uses the read module 1912 toservice or satisfy read requests for data. The read module 1912, inresponse to the mapping module 1904 determining that the namespaceidentifier of a read request is mapped to the auto-commit buffers 1013,reads the data specified in the read request (e.g., data at a specifiedoffset within a file, or the like) directly from the mapped location inthe auto-commit buffers 1013 from user-space, bypassing or skipping anoperating system or kernel storage stack. If the mapping module 1904determines that the namespace identifier of the read request is notmapped to or associated with the auto-commit buffers 1013, the readmodule 1912 may read the data from the non-volatile memory media 1110.The bypass module 1906 may use the read module 1912 to return the readdata to a requesting client such as an ACM user 1016, mapping or copyingthe read data into virtual memory for the requesting client, sending thedata to the requesting client, or the like.

In one embodiment, the bypass module 1906 uses the write module 1914 toservice or satisfy write requests for data. In response to the mappingmodule 1904 determining that the namespace identifier of a write requestis mapped to the auto-commit buffers 1013, the write module 1914 maywrite the data specified in the write request directly to the mappedlocation in the auto-commit buffers 1013 from user-space, bypassing orskipping an operating system or kernel storage stack. If the mappingmodule 1904 determines that the namespace identifier of the writerequest is not mapped to or associated with the auto-commit buffers1013, the write module 1914 may write the data to the non-volatilememory media 1110. The write module 1914 may read or copy the write datafrom virtual memory for the requesting client, sending the data to theauto-commit buffers 1013 and/or the non-volatile memory media 1110, orthe like.

In one embodiment, the has-been-written module 1908 may track whichportions of data of the auto-commit buffers 1013 have been updated, arenot yet stored in the non-volatile memory media 1110, or the like. Incertain embodiments, portions of the data of the auto-commit buffers1013 may already be stored in and/or committed to the non-volatilememory media 1110. In response to a restart event or another committrigger, it may be more efficient for the auto-commit buffers 1013 tocommit, flush, or destage just data that is not already stored in thenon-volatile memory media 1110, instead of committing all of the data.Further, the commit agent 1020 may need to know which portions of a pageor other storage region have been updated in order to recover the pageor other storage region after a restart event.

Similarly, reading an entire page's contents back into the auto-commitbuffers 1013 from the backing non-volatile memory media 1110 may also bean expensive or time consuming operation. For example, if the cost ofreading the page contents in from the non-volatile memory media 1110 is50 us, and each write to the auto-commit buffers 1013 takes 500 ns orless, even if the page is written 100 times after the initial read—thecost of the initial read will still represent 50% of the latencyassociated with accessing the page.

The has-been-written module 1908 may track which data in the auto-commitbuffers 1013 has been updated and is not stored by the non-volatilememory media 1110, which data is already stored in the non-volatilememory media 1110, or the like. For example, the has-been-written module1908 may maintain a bitmap or other data structure such as a bitmap,bitmask, bit field, table, vector, or the like, populated withindicators of which data has been updated since the data was loaded,since a previous commit operation, or the like. The has-been-writtenmodule 1908, periodically or in response to a restart event, may persista has-been-written bitmap or other data structure to the non-volatilememory media 1110, and the has-been-written module 1908 may cooperatewith the commit agent 1020 to merge updates to data and/or differentversions of data. In one embodiment, the has-been-written module 1908allows the auto-commit buffers 1908 to commit or copy just data that hasbeen updated, in response to a commit trigger or restart event, and thecommit agent 1020 may merge the updates with a previous version of thedata preserved in a sequential log of the non-volatile memory media 1110after recovery from the restart event or the like.

In one embodiment, the has-been-written module 1908 associates ahas-been-written bitmap or other has-been-written metadata with each ACMpage of the auto-commit buffers 1013. The has-been-written module 1908may track updates or changes to data in the auto-commit buffers 1013 ata byte-level, with a bit in a has-been-written bitmap for each byte orthe like, indicating whether or not the corresponding byte has beenwritten or updated. Upon destaging, instead of using a read modifywrite, the controller 1104 may cooperate with the has-been-writtenmodule 1908 to identify updated regions of the page, allowing sub-blockwrites or the like.

In one embodiment, the has-been-written module 1908 may provide ACMusers 1016 with access to has-been-written bitmaps. For example, an ACMpage of the ACM buffers 1013 may store a last page/block of a log file.Each update to the ACM page may increase the size of the file. Insteadof noting and storing each change to the file length, to reduce theoverhead of system calls, a has-been-written bitmap from thehas-been-written module 1908 may be used to derive a new file lengthwhile maintaining the ACM 1011 efficiency.

In a further embodiment, the has-been-written module 1908 may maintainone or more has-been-written data structures at a sub-page granularity,such as a byte granularity, an error correcting code (ECC) chunk orblock granularity, or the like. A has-been-written data structure, incertain embodiments, may allow the commit agent 1020 or the like todetermine what data within a page is dirty and not stored by thenon-volatile memory media 1110, if there are holes in a range of datadue to out-of-order delivery, or the like.

The has-been-written module 1908, in certain embodiments, providesaccess to a has-been-written data structure using memory access (e.g.,load/store semantics), provides a “clear-all” byte to clear a set ofhas-been-written bits at once, or the like. The has-been-written module1908 may clear or reset has-been-written metadata from ahas-been-written data structure in response to the auto-commit buffers1013 committing, destaging, flushing, or otherwise copying the data tothe non-volatile memory media 1110. The has-been-written module 1908, inone embodiment, may use a has-been-written data structure stored involatile memory to locate data to commit, destage, or flush to thenon-volatile memory media 1110 without accessing or reading thenon-volatile memory media 1112, preventing an extra read-modify-writeoperation or the like.

The has-been-written module 1908, in one embodiment, maintains thehas-been-written data structure such that it parallels every byte ofvirtual memory with a corresponding bit that automatically indicateswhich bytes have indeed had data “stored” to them, been written, beenmodified, been updated, or the like.

In certain embodiments, the has-been-written module 1908 and/or the SML1050 may provide one or more has-been-written data structures as part ofa persistent storage namespace itself, such as a filesystem namespace, alogical unit number (LUN) namespace, or the like. For example, thehas-been-written module 1908 and/or the SML 1050 may provide ahas-been-written data structure as a “shadow file” or the like that isdesignated to contain the bitmask of another file. ACM users 1016 mayperform MMIO writes or other operations for both of these files orpages. In another embodiment, a has-been-written data structure may beinterleaved within the data it represents, such as a 512 byte bitmaskinterleaved after each 4 kibibyte block within the same file, or thelike.

In one embodiment, the security module 1910 is configured to provideaccess controls, enforce permissions, protect against attacks, or thelike for data stored in the auto-commit buffers 1013 and/or thenon-volatile memory media 1110. Because the ACM module 1317 may provideaccess to the ACM buffers 1013 in user-space, the ACM buffers 1013 maybe susceptible to denial-of-service (DoS) or other attacks. For example,an ACM user 1016 may maliciously monopolize bandwidth of thecommunications bus 1040, such as a PCIe bus or the like. The securitymodule 1910, in one embodiment, monitors or tracks traffic on thecommunications bus 1040, access to each page of the auto-commit buffers1013, or the like. The security module 1910, in a further embodiment,may disable access to an ACM user 1016 by unmapping an ACM page of datafrom the ACM user's virtual memory in response to the monitored accessto the ACM page in virtual memory exceeding a traffic threshold, or thelike.

As described above, a user-space library, process, or application may bean untrusted entity. In certain embodiments, file system accesspermissions that are normally enforced by the operating system or kernelin kernel-space, may be bypassed by the bypass module 1906, whichoperates in user-space as described above. To present this fromhappening, in one embodiment, the security module 1910 is configured touse virtual memory access controls to enforce file system accesspermissions associated with data files of the auto-commit buffers 1013mapped or copied into virtual memory. For example, if the file accesspermission for a file stored in an ACM page is read-only, the securitymodule 1910 may cooperate with the mapping module 1904 to map the ACMpage into virtual memory as read-only. As described above, in certainembodiments, the mapping module 1904 performs mappings in kernel-space,which may allow the security module 1910 to maintain access controls,even if the bypass module 1906 provides access in user-space.

As described above, once data has been stored in the auto-commit buffers1013, the ACM 1011 preserves or persists the data in non-volatile memorymedia 110, 1110 and provides the data from the non-volatile memory media110, 1110 to clients, such as ACM users 1016, after recovery from therestart event.

The ACM module 1317 and its various sub-modules 1902, 1904, 1906, 1908,1910, 1912, 1914 as described above, may be disposed in a device driverfor the ACM 1011 executing on a processor 1012 of the host device 1014,such as the SML 1050, may be disposed in a storage controller 104, 1004,1104, 1304 for the ACM 1011, and/or may comprise portions in each of adevice driver and a storage controller 104, 1004, 1104, 1304, or thelike

FIG. 11 depicts one embodiment of an address mapping structure 2000, alogical address space 2120, and a sequential, log-based, append-onlywriting structure 2140. The address mapping structure 2000, in oneembodiment, is maintained by the storage controller 104, 1004, 1104,1304, the storage management layer 1050, a logical-to-physicaltranslation layer or address mapping structure, or the like to map LBAsor other logical addresses to physical locations on the non-volatilestorage media 1110. While the depicted embodiment is described withregard to the non-volatile storage media 1110, in other embodiments, theaddress mapping structure 2000 may map namespace identifiers for theauto-commit buffers 1013 or the like. The address mapping structure2000, in the depicted embodiment, is a B-tree with several entries. Inthe depicted embodiment, the nodes of the address mapping structure 2000include direct references to physical locations in the non-volatilestorage device 1102. In other embodiments, the address mapping structure2000 may include links that map to entries in a reverse map, or thelike. The address mapping structure 2000, in various embodiments, may beused either with or without a reverse map. In other embodiments, thereferences in the address mapping structure 2000 may includealpha-numerical characters, hexadecimal characters, pointers, links, andthe like.

The address mapping structure 2000, in the depicted embodiment, includesa plurality of nodes. Each node, in the depicted embodiment, is capableof storing two entries. In other embodiments, each node may be capableof storing a greater number of entries, the number of entries at eachlevel may change as the address mapping structure 2000 grows or shrinksthrough use, or the like.

Each entry, in the depicted embodiment, maps a variable length range ofLBAs of the non-volatile storage device 1102 to a physical location inthe storage media 1110 for the non-volatile storage device 1102.Further, while variable length ranges of LBAs, in the depictedembodiment, are represented by a starting address and an ending address,in other embodiments, a variable length range of LBAs may be representedby a starting address and a length, or the like. In one embodiment, thecapital letters ‘A’ through ‘M’ represent a logical or physical eraseblock in the physical storage media 1110 of the non-volatile storagedevice 1102 that stores the data of the corresponding range of LBAs. Inother embodiments, the capital letters may represent other physicaladdresses or locations of the non-volatile storage device 1102. In thedepicted embodiment, the capital letters ‘A’ through ‘M’ are alsodepicted in the log-based writing structure 2140 which represents thephysical storage media 1110 of the non-volatile storage device 1102.

In the depicted embodiment, membership in the address mapping structure2000 denotes membership (or storage) in the non-volatile storage device1102. In another embodiment, an entry may further include an indicatorof whether the non-volatile storage device 1102 stores datacorresponding to a logical block within the range of LBAs, data of areverse map, and/or other data.

In the depicted embodiment, the root node 2008 includes entries 2102,2104 with noncontiguous ranges of LBAs. A “hole” exists at LBA “208”between the two entries 2102, 2104 of the root node. In one embodiment,a “hole” indicates that the non-volatile storage device 1102 does notstore data corresponding to one or more LBAs corresponding to the“hole.” In one embodiment, the non-volatile storage device 1102 supportsblock I/O requests (read, write, trim, etc.) with multiple contiguousand/or noncontiguous ranges of LBAs (e.g., ranges that include one ormore “holes” in them). A “hole,” in one embodiment, may be the result ofa single block I/O request with two or more noncontiguous ranges ofLBAs. In a further embodiment, a “hole” may be the result of severaldifferent block I/O requests with LBA ranges bordering the “hole.”

In the depicted embodiment, similar “holes” or noncontiguous ranges ofLBAs exist between the entries 2106, 2108 of the node 2014, between theentries 2110, 2112 of the left child node of the node 2014, betweenentries 2114, 2116 of the node 2018, and between entries of the node2118. In one embodiment, similar “holes” may also exist between entriesin parent nodes and child nodes. For example, in the depictedembodiment, a “hole” of LBAs “060-071” exists between the left entry2106 of the node 2014 and the right entry 2112 of the left child node ofthe node 2014.

The “hole” at LBA “003,” in the depicted embodiment, can also be seen inthe logical address space 2120 of the non-volatile storage device 1102at logical address “003” 2130. The hash marks at LBA “003” 2140represent an empty location, or a location for which the non-volatilestorage device 1102 does not store data. The “hole” at LBA 2134 in thelogical address space 2120, is due to one or more block I/O requestswith noncontiguous ranges, a trim or other deallocation command to thenon-volatile storage device 1102, or the like. The address mappingstructure 2000 supports “holes,” noncontiguous ranges of LBAs, and thelike due to the sparse and/or thinly provisioned nature of the logicaladdress space 2120.

The logical address space 2120 of the non-volatile storage device 1102,in the depicted embodiment, is sparse and/or thinly provisioned, and islarger than the physical storage capacity and corresponding storagedevice address space of the non-volatile storage device 1102. In thedepicted embodiment, the non-volatile storage device 1102 has a 64 bitlogical address space 2120 beginning at logical address “0” 2122 andextending to logical address “264-1” 2126. Because the storage deviceaddress space corresponds to only a subset of the logical address space2120 of the non-volatile storage device 1102, the rest of the logicaladdress space 2120 may be allocated, mapped, and used for otherfunctions of the non-volatile storage device 1102.

The sequential, log-based, append-only writing structure 2140, in thedepicted embodiment, is a logical representation of the physical storagemedia 1110 of the non-volatile storage device 1102. In certainembodiments, the non-volatile storage device 1102 stores datasequentially, appending data to the log-based writing structure 2140 atan append point 2144. The non-volatile storage device 1102, in a furtherembodiment, uses a storage space recovery process, such as a garbagecollection module or other storage space recovery module that re-usesnon-volatile storage media 1110 storing deallocated/unused logicalblocks. Non-volatile storage media 1110 storing deallocated/unusedlogical blocks, in the depicted embodiment, is added to an availablestorage pool 2146 for the non-volatile storage device 1102. By clearinginvalid data from the non-volatile storage device 1102, as describedabove, and adding the physical storage capacity corresponding to thecleared data back to the available storage pool 2146, in one embodiment,the log-based writing structure 2140 is cyclic, ring-like, and has atheoretically infinite capacity.

In the depicted embodiment, the append point 2144 progresses around thelog-based, append-only writing structure 2140 in a circular pattern2142. In one embodiment, the circular pattern 2142 wear balances thenon-volatile storage media 122, increasing a usable life of thenon-volatile storage media 1110. In the depicted embodiment, a garbagecollection module or other storage capacity recovery process has markedseveral blocks 2148, 2150, 2152, 2154 as invalid, represented by an “X”marking on the blocks 2148, 2150, 2152, 2154. The garbage collectionmodule, in one embodiment, will recover the physical storage capacity ofthe invalid blocks 2148, 2150, 2152, 2154 and add the recovered capacityto the available storage pool 2146. In the depicted embodiment, modifiedversions of the blocks 2148, 2150, 2152, 2154 have been appended to thelog-based writing structure 2140 as new blocks 2156, 2158, 2160, 2162 ina read, modify, write operation or the like, allowing the originalblocks 2148, 2150, 2152, 2154 to be recovered.

FIG. 12 depicts one embodiment of a method 2200 for providing access toauto-commit memory 1011. The method 2200 begins, and the request module1902 receives 2202 a request for data. The request may include anamespace identifier for the data. The mapping module 1904 identifies2204 a relationship between the namespace identifier and an auto-commitbuffer 1013. The bypass module 1906 satisfies 2206 or services thereceived 2202 request using the auto-commit buffer 1013 in response tothe identified 2204 relationship associating the namespace identifierwith the auto-commit buffer 1013 and the method 2200 ends.

FIG. 13 depicts another embodiment of a method 2300 for providing accessto auto-commit memory 1011. The method 2100 begins, and the requestmodule 1902 determines 2302 whether a request for data of thenon-volatile memory device 1102 has been received. Once the requestmodule 1902 determines 2302 that a request has been received, themapping module 1904 determines 2304 whether the data, a namespaceidentifier or other logical identifier, or the like of the request isassociated with the auto-commit memory 1011.

If the mapping module 1904 determines 2304 that the data of the requestis not associated with the auto-commit memory 1011, the mapping module1904 determines 2306 whether to associate the data with the auto-commitmemory 1011. If the mapping module 1904 determines 2306 to associate thedata with the auto-commit memory 1011, the mapping module 1904 maps 2308or associates the data of the request with the auto-commit memory 1011,otherwise the storage controller 1104 satisfies 2312 or services thereceived 2302 request from the non-volatile memory media 1110. Themapping module 1904 may map 2308 the data or cause the data to be mapped2308 to the auto-commit memory 1011 from kernel-space.

If the mapping module 2304 determines 2304 that the data of the received2302 request is associated with the auto-commit memory 1011 or if themapping module 2304 determines 2306 to map 2308 the data to theauto-commit memory 1011, the bypass module 1906 satisfies 2310 orservices the received 2302 request directly from the auto-commit memory1011, bypassing an operations system or kernel storage stack or the liketo satisfy 2310 the request from user-space. The request module 1902continues to monitor 2302 or otherwise receive or intercept requests fordata of the non-volatile memory device 1102.

A means for associating a logical identifier or other namespaceidentifier with a page of auto-commit memory 1011, in variousembodiments, may include a storage management layer 1050, a devicedriver, a storage controller 104, 1004, 1104, 1304, a mapping module1904, other logic hardware, and/or other executable code stored on acomputer readable storage medium. Other embodiments may include similaror equivalent means for associating a namespace identifier with a pageof auto-commit memory 1011.

A means for bypassing an operating system storage stack to satisfy astorage request for data of a page of auto-commit memory 1011, invarious embodiments, may include a storage management layer 1050, adevice driver, a storage controller 104, 1004, 1104, 1304, a mappingmodule 1904, other logic hardware, and/or other executable code storedon a computer readable storage medium. Other embodiments may includesimilar or equivalent means for bypassing an operating system storagestack to satisfy a storage request for data of a page of auto-commitmemory 1011.

A means for preserving data of a page of auto-commit memory 1011 inresponse to a failure condition or restart event, in variousembodiments, may include a secondary power supply 124, 1024, 1324, anauto-commit memory 1011, 1111, an auto-commit buffer 1013, a commitagent 1020, a commit management module 1122, a commit module 1320, anACM module 1317, other logic hardware, and/or other executable codestored on a computer readable storage medium. Other embodiments mayinclude similar or equivalent means for preserving data of a page ofauto-commit memory 1011 in response to a failure condition.

A means for providing access to preserved data after a failure conditionor restart event, in various embodiments, may include a non-volatilestorage device 102, a non-volatile memory media 110, 1110, 1310, 1502, astorage management layer 1050, a commit agent 1020, an auto-commitmemory 1011, 1111, an auto-commit buffer 1013, logic hardware, and/orother executable code stored on a computer readable storage medium.Other embodiments may include similar or equivalent means for providingaccess to preserved data after a failure condition or restart event.

The present disclosure may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the disclosure is, therefore,indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A method comprising: receiving a write requestfor data, the write request comprising a namespace identifier;identifying a relationship between the namespace identifier and one ormore of a memory and a non-volatile memory medium; servicing the writerequest using the memory in response to the identified relationshipassociating the namespace identifier with the memory; and servicing thewrite request using the non-volatile medium in response to theidentified relationship associating the namespace identifier with thenon-volatile medium.
 2. The method of claim 1, wherein a user spacedevice driver services the write request using the memory directly bybypassing an operating system storage stack.
 3. The method of claim 1,wherein identifying the relationship between the namespace identifierand one or more of the memory and the non-volatile memory mediumcomprises determining whether the write request comprises an auto-commitflag associating the namespace identifier with the memory.
 4. The methodof claim 1, wherein servicing the write request using the memorycomprises mapping the data into virtual memory of a requesting client.5. The method of claim 4, further comprising unmapping the data fromvirtual memory in response to access to the virtual memory exceeding atraffic threshold for the virtual memory.
 6. The method of claim 1,further comprising, arming the memory with metadata specifying a logicalblock address of a non-volatile medium to which the data of the memoryis to be committed in response to a predefined trigger, wherein thenamespace identifier is persistently mapped to the logical blockaddress; and committing the data of the memory to the logical blockaddress of the non-volatile medium in response to detecting the trigger.7. The method of claim 1, further comprising, tracking which portions ofdata of the memory have been updated; and committing the updatedportions of data of the memory to a non-volatile medium separately fromnon-updated portions in response to detecting a predefined trigger. 8.The method of claim 1, wherein the namespace identifier is a member of apersistent namespace, the persistent namespace is configured to survivea restart event, and the persistent namespace configured to grant aclient access to data of the namespace identifier subsequent to therestart event.
 9. The method of claim 8, wherein the persistentnamespace comprises a logical unit number (LUN) namespace for a storagedevice and the namespace identifier comprises a LUN address within theLUN namespace.
 10. The method of claim 8, wherein the persistentnamespace comprises a file system namespace and the namespace identifiercomprises a file identifier of the file system namespace.
 11. The methodof claim 1, wherein identifying the relationship between the namespaceidentifier and the memory comprises one of identifying an existingrelationship between the namespace identifier and the memory, andcreating a relationship between the namespace identifier and the memory.12. The method of claim 1, wherein the relationship associates thenamespace identifier with the memory in response to one or more ofdetecting an existing relationship between the namespace identifier andthe memory; detecting an auto-commit flag for the write request; anddynamically assigning the namespace identifier for association with thememory.
 13. The method of claim 1, wherein the memory is within anisolation zone of a non-volatile device comprising a non-volatile mediumand the isolation zone is configured to receive power from a secondarypower source.
 14. The method of claim 13, wherein a storage capacity ofa plurality of memory buffers, including the memory, within theisolation zone is selected such that a power hold-up time provided bythe secondary power source allows the plurality of memory buffers tocommit data to a non-volatile medium during the power hold-up time inresponse to a restart event.
 15. An apparatus comprising: an auto-commitmemory module configured to cause a volatile memory buffer to commitdata from the volatile memory buffer to a non-volatile memory medium inresponse to the data filling at least a threshold amount of the volatilememory buffer; a mapping module configured to determine whether toassociate a range of addresses for data with the volatile memory bufferor the non-volatile memory medium; and a bypass module configured toservice a request for the range of addresses directly using the volatilememory buffer in response to the mapping module determining to associatethe range of addresses with the volatile memory buffer and furtherconfigured to service the request for the range of addresses using thenon-volatile memory medium in response to the mapping module determiningto associate the range of addresses with the non-volatile memory medium,the request comprising a write request.
 16. The apparatus of claim 15,further comprising a request module configured to receive the requestfor the range of addresses for data, the mapping module configured todetermine to associate the range of addresses for data with the volatilememory buffer in response to an auto-commit flag of the request.
 17. Theapparatus of claim 15, further comprising a request module configured tointercept requests for the non-volatile memory medium, the mappingmodule configured to dynamically determine to associate the range ofaddresses for data with the volatile memory buffer in response to therequest module intercepting the request for the range of addresses. 18.The apparatus of claim 15, wherein the bypass module is configured toservice the request for the range of addresses for data directly fromthe volatile memory buffer by bypassing a kernel storage stack andservicing the request from user-space.
 19. The apparatus of claim 15,wherein the request for the range of addresses for data comprises awrite request and the bypass module is configured to service the writerequest by copying data of the write request into a virtual memorylocation of a requesting client in response to the mapping moduledetermining to associate the range of addresses for data with thevolatile memory buffer, the virtual memory location backed by thevolatile memory buffer.
 20. A system comprising: a storage devicecomprising one or more auto-commit pages configured to preserve data ofthe auto-commit pages in a non-volatile memory medium in response to arestart event; and a device driver for the storage device, the devicedriver configured to cause data of the storage device to be mapped, fromkernel-space, into virtual memory and to service a write request, fromuser-space, the device driver using the one or more auto-commit pages toservice the write request in response to determining an association ofthe write request with the one or more auto-commit pages and using thenon-volatile memory medium to service the write request in response todetermining an association of the write request with the non-volatilememory medium.
 21. The system of claim 20, further comprising a hostassociated with the virtual memory, the host comprising a processor incommunication with the storage device, the device driver executing onthe processor.
 22. A computer program product comprising anon-transitory computer readable storage medium storing computer usableprogram code executable to cause a computer to perform operations, theoperations comprising: intercepting, in user-space, a storage requestfor a memory device, the storage request comprising a file identifierand an offset for a write operation; determining whether the offset andthe file identifier are mapped to the volatile memory; servicing thestorage request in user-space directly using a volatile memory of thememory device in response to determining that the offset and the fileidentifier are mapped to the volatile memory; determining whether theoffset and the file identifier are mapped to a non-volatile memory ofthe memory device; and servicing the storage request in user-space usingthe non-volatile memory of the memory device in response to determiningthat the offset and the file identifier are mapped to the non-volatilememory.
 23. The computer program product of claim 22, wherein theoperations further comprise enforcing file system access permissions fordata of the offset and the file identifier using virtual memory accesscontrols.
 24. An apparatus comprising: means for associating a logicalidentifier with one of a volatile memory and a non-volatile memorymedium; means for bypassing an operating system storage stack to servicea storage request for data associated with the logical identifier usingthe volatile memory in response to the logical identifier beingassociated with the volatile memory and using the non-volatile memorymedium in response to the logical identifier being associated with thenon-volatile memory medium; and means for preserving the data of thevolatile memory in the non-volatile memory medium in response to afailure condition.
 25. The apparatus of claim 24, further comprisingmeans for providing access to the preserved data after the failurecondition.